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3. §1 - Definition

The Definition - between 50 & 150/200 words long. This is the first text read by the majority of people reaching the article page. What should we be aiming to say? - what should we aim not to say? - from those two points we can work out what we are going to say. SFC9394 10:40, 28 September 2006 (UTC)

Actually what we want, I suppose, is to define the lead paragraphs. They will of course include, but are not restricted to, a definition of physics --MichaelMaggs 12:08, 28 September 2006 (UTC)

Statement defining the audience? Everyone? The eleven-year-old? College grads? --Ancheta Wis 17:29, 28 September 2006 (UTC)

Everybody hopefully. First should come a definition that is easy to understand, and then one that is more rigorous. Krea 18:36, 28 September 2006 (UTC)

No suggestions yet. This is proving difficult. How about looking at the text that's used on the current Physics page, and saying what we think is wrong with it. That might give us some pointers. The current text is:

Physics (from the Greek, φύσις (phúsis), "nature" and φυσική (phusiké), "knowledge of nature"), the most fundamental physical science, is concerned with the underlying principles of the natural world. Consequently, physics deals with the elementary constituents of the Universe — that is, all classes of matter and energy — and their interactions, as well as the analysis of systems which are best understood in terms of these fundamental principles. --MichaelMaggs 14:43, 29 September 2006 (UTC)

Oooh, that's just asking for it!

What does "most fundamental physical science" mean? For one thing, taking the population as a whole, the word "fundamental" can be quite subjective. I think we should try to use as basic a set of concepts as possible, like talking about physics in terms of knowledge (which is itself a tricky subject).
The word "underlying" is making an implicit assumption about nature itself: that its laws are hidden from us. Now, for all we know, there is no evidence to suggest that this is the way it had to be and, conversely, no evidence for the contrary. We must ask ourselves if it is reasonable to assume a universe to exist in which this were not true. Therefore, is it reasonable to conclude that this statement is an observation of nature itself and thus should not be included in the definition?
I'm not sure that, "physics deals with the elementary constituents of the Universe," is a consequence of physics being "...concerned with the underlying principles of the natural world."

I could continue, but these complaints suffice to outline the point that I would like to make: I think that we must strive to formulate a definition that is as fundamental as possible. In other words, a definition that makes the least amount of assumptions about nature. For the sake of creating a constructive discussion, let me introduce the following definition of physics:

Physics is the body of statements that assert the manner in which nature truly behaves.

Now, I ask you: are you happy with this definition? I imagine that you will not be, but why? Is this not the most general definition we can make? Krea 17:05, 29 September 2006 (UTC)

Comment here 00:07, 30 September 2006 (UTC), Ancheta Wis

What 'the' body of statements is should be clarified. But I don't agree with the definition's perspective. Science is more than the product. Science is a certain method of study, and physics is a science concerned with a certain topic (matter and energy). "Physics is the science concerned with the discovery and understanding of the true and fundamental laws which govern matter [and energy]" is my suggestion. Directly after this, we should elaborate on the constraints (how it's different from other sciences - chemistry is about atoms, aren't they the same then? if we understand matter, we'll be able to know how people work too, right?) "Physics differs from... in that...", "While other sciences...". Then, on the variety of what physics encompasses: "The motion of galaxies and composition of atoms, gravity, light, and the nature of time and space are all in the domain of physics". The second paragraph could offer a brief history covering the most important achievements and some of the most important research going on today. –M^T 08:16, 2 October 2006 (UTC)

I prefer "Physics is the study of (or maybe "search for") the mechanisms and behavior of the natural world." for an introductory sentence. Saying anything about fundamentals and how true something is somewhat conceited and not entirely accurate - in my experience, physics appears to be more of an attempt to quantify/predict how something will act, and from there the understanding of the laws governing those actions is derived. Since physical scientists have produced a number of theories in the past which were wrong and/or incomplete (for a variety of reasons, not always their fault), saying that physics is the "true" form of the art isn't exactly accurate. There's also an old joke about fundamental science I'm not going to repeat here, but saying physics is "fundamental" (while a decent descriptor IMO) is a nebulous and ultimately POV way of putting physicists on a pedestal over other scientists. As far as the intended age thing goes, I would venture any pre-college grad (training in physics, not in general) - it's unlikely anyone with a physics degree would just up and read the "physics" Wiki article and expect it to contain something at their level. —Preceding unsigned comment added by Virogtheconq (talk • contribs)

So how about the following operational definition of physics. It shows that we must search and do other work to understand the world, that our understanding does not come for free; that the more we know, the more we can hope to understand, and vice versa. --Ancheta Wis 23:21, 3 October 2006 (UTC)

"Physics is the search for the mechanisms and behavior of the natural world." [part of the above comment]

I disagree with these definitions. Physics doesn't search for behaviour, it tries to determine and understand what causes the observed behaviour. In my definition, "Physics is the science concerned with the discovery and understanding of the ~~true and~~ fundamental laws which govern matter [and energy]" "true" is perhaps redundant with "science", but fundamental is the proper word. We're not implying that physics is fundamental, we're implying that physics attempts to discover those underlying, fundamental laws from which emerge all of the complexity (and complex laws) around us. It's an important thing to note. I can think of no way to express that that isn't tinged with an implication that other matter/energy laws are based on physics - which is a sure truth, they are. If we had a way to state this without the implication, then great, but an accurate description should not be sacrificed for the sake of soothing other scientists because the occasional reader doesn't quite understand the difference between "fundamental" and "important". Note that I'm not at all a physicist - this isn't bias speaking. –M^T 00:40, 4 October 2006 (UTC)

Welcome to the discussion M, especially since you can give a non-physicist's point of view, which is very welcome. Now, the fact that you are not a physicist is clear (it was definately clear when you mentioned it!) because your definition refers specifically to "matter and energy". In my opinion, these concepts should not be contained in the definition because it is no way known whether they are fundamental to the existence of physics. The definition should be as general as we can make it. Thus, intead of talking about searching for the behaviour of this or that, we should just say that we are searching for the behaviour of something, anything, which we do not wish to specify. When you say, "Physics doesn't search for behaviour, it tries to determine and understand what causes the observed behaviour," the thing that "causes behaviour" is itself behaviour! Furthermore, Let me expain why I don't agree with your definition:

Physics is the science concerned with the discovery and understanding of the true and fundamental laws which govern matter [and energy]."

Physics is indeed a science. But did it have to be? What do I mean? Well, what is science? Answer: A science is an application of the scientific method. So what? Well, to be a science, the thing itself must not be known - we have to make observations about it. Now, suppose that we already knew the laws of nature - there is no known reason why this should not be possible. Thus, if we did have this knowledge, physics would no longer be a science. Thus, the statement that physics is a science is not as general as it may be. The observation that physics is indeed a science is a particular of our universe (as far as anybody knows).
I've already mentioned that we should remove the words "matter" and "energy" from the definition, and replace them with unspecified entities under the generic name "nature", or something similar.

Thus, what are we left with?

Physics is ~~the science~~ concerned with the discovery and understanding of the fundamental laws which govern ~~matter [and energy]~~ nature."

Which is esentially what I first suggested. So, let me state it again (with some suggested changes):

Physics is the body of, or method of obtaining, statements that assert the manner in which nature truly behaves.

Krea 22:40, 9 October 2006 (UTC)

Krea - I rather fear that in your eagerness to be as general as possible you are in danger of losing most if not all readers in metaphysical or philosophical niceties. You question, for example, whether physics has to be a science, and argue that in a hypothetical world in which we knew all the answers physics would no longer be such. You may be right, but in our own world we don't and it most certainly is. Since there's no question about it, I can't see any reason not to describe physics as a science.

We should, in my view, be quite comfortable in using the terms matter and energy. They are both commonly-understood expressions which help the uninitiated reader get an immediate sense of what this thing called physics is all about. Although there's no formally-agreed definition of physics, any more than there is of most sciences, I'd be willing to bet that the majority of physicists would use one or both of those terms if asked to describe physics in a nutshell. And how physicists describe their own field is most definitely of relevance. It goes without saying that non-physicists are most welcome here, and have already contributed significantly to the discussion, but it's hard to accept the implication in an earlier statement (not one of yours) that that a physicist's viewpoint would show 'bias'. Without the input of physicists an article entitled "Physics" is likely to be a poor thing indeed. We need both views.

You have suggested that the initial sentence of the lead para should read "Physics is the body of, or method of obtaining, statements that assert the manner in which nature truly behaves". But by avoiding words such as matter and energy, which are specific to physics, your definition covers almost any type of scientific reasearch. Research into the mating habits of King Penguins, for example, would seem a good example of "research into the manner in which nature truly behaves".

I suggest something along the following lines. As we are meant to be discussing all the lead paragraphs, not just the first sentence, I have made a proposal for the entire thing: --MichaelMaggs 12:26, 10 October 2006 (UTC)

Krea, I enjoy the correctness of your definition, but I disagree with it. This section 16 of The Elements of Style presents my case. This isn't simply a manner of artistic style, but one of comprehension. "Science", "laws", and "matter and energy" are clearly understood by readers; what exactly is meant by "statements that assert the manner[…]" and "nature" is not so readily understood. The full coverage that your definition attempts to make is best reserved for the body of the article, or better yet, the reader's own common sense and experience. –M^T 21:06, 10 October 2006 (UTC)

Oddly enough, the fact that you "enjoy the correctness of [my] definition" brings to me more pleasure than the fact that you "...disagree with it" brings me distress! I agree that it's a little dictionary-esque in style, but it's not completely beyond the realms of comprehension is it? I don't mind having a definition that the non-physicist will understand (in fact, I think this is absolutely necessary), but I would also like to have one that is pedantically "rigorous" and "correct". I don't like MichaelMaggs' definition in its current form because parts of it are plain wrong and misleading, and it includes no acknowledgment of this. Prime example: "Physics is the branch of science concerned with the properties of matter and energy, and the relationships between them." Now, this is wrong: what about the Lagrangian? Properties of the Lagrangian of a system also constitute physics; but the Lagrangian falls under neither the topics of matter nor energy. It is also misleading: energy and matter are not concepts of physics more fundamental than any others as one may be led to think. My point is that it is irresponsible to only include a lay definition or to leave it to "...the reader's own common sense and experience." The article has a duty to appeal to all readers. Therefore to omit my definition is as bad as having it as the only one. What do you say to including both? Krea 22:14, 10 October 2006 (UTC)

It's comprehensible, but my objection is that the definition shouldn't worry too much about being perfect. "Matter and energy" seems to be the best we have, without a paragraph-long elaboration, and without a general word like "nature" (the laws of nature may refer to just about anything natural). I like "matter" because it's bland. You can't mistake it for the study of penguins and other complex things that incidentally are made of matter. Yes, some physics isn't concerned directly with matter, but that detail should probably be pointed out in the body. I think that it harms us to think of it as a definition. Instead we should think of it as an introduction. Sketch the outline, and then fill in the details with the rest of the article. –M^T 23:02, 10 October 2006 (UTC)

"...the definition shouldn't worry too much about being perfect"!!! That's a horrible thing for any mathematical physicist to have to read. What you said you want is just personal opinion - I imagine that aiming for a definition that is not as good as we can make it will annoy a lot of people here. Ok, let's stop and take things in. You want comprehensibilty, right? I want rigour. Why not have both? Definitions need to be placed in the definitions section, nowhere else. All we say is: "physics, in lay terms, is the study of matter + energy..." or whatever. Then we say that, "A more rigourous definition of physics, however, is..." What's wrong with that? Krea 12:57, 11 October 2006 (UTC)

To begin with, I agree that matter and energy should not be mentioned specifically by themselves. What about space/time? What is special about matter? To destingush it from other sciences it needs something like fundemental or underlying or mathematical. David R. Ingham 00:15, 15 October 2006 (UTC)

"Physics is the most basic of all the sciences. Within it, the basic laws of natural forces, such as gravity, are formed; as well, the interaction between inanimate objects is observed. Specifically, the interactions between matter, energy, and time are concerned." It's a start. However, I do agree that a general definition should be given. After all, it is only the introduction. Yet, physics is rather hard to define. :( Jerr 23:42, 16 October 2006 (UTC)

Proposal for lead paragraphs

Physics is the branch of science concerned with the properties of matter and energy, and the relationships between them. It seeks to understand and describe the physical properties of the universe at the most fundamental level possible, normally by way of mathematical modelling of the behaviour of physical systems. Physics is accordingly closely allied to mathematics, which provides the logical framework in which these descriptions can be precisely formulated. More generally, the aim is to go beyond simply describing physical phenomena mathematically, but rather to construct mathematical models or theories which can also make predictions about the way in which a physical system is expected to behave in certain defined circumstances. These predictions can then be experimentally tested to support or refute the theory.

Some of the mathematical theories of physics are believed to be common to all physical systems. These are often referred to as the laws of physics, although the word 'law' is a misnomer since even a law of physics could, in principle, be disproved by experiment. Others theories are more limited in that they describe the behaviour of specific physical systems only, or are applicable only within a defined range.

Classical physics traditionally included the fields of mechanics, optics, electricity, magnetism, acoustics and heat. The more recently-discovered fields of general and special relativity are also normally considered to fall within in this category. Modern Physics is less well-defined but is usually taken to cover fields which rely on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics, solid state physics and condensed matter physics. The description is, however, of limited practical use since quantum effects are nowadays known to be of importance even in many fields previously considered to be purely classical.

Physics research is divided into two main branches, namely experimental physics and theoretical physics. Experimental physics focuses mainly on empirical research, and on the creation and testing of theories against practical experiment. Theoretical physics is more closely allied to mathematics, and involves creating and working through the mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available. Most theoretical physicists work on aspects of particle physics and allied fields.

--MichaelMaggs 12:22, 10 October 2006 (UTC)

Well-put. There is much to say of its merits, but I won't focus there as it won't get us far. Some things are best left unsaid. I'll edit it, revert, link the diff, and elaborate. Here's the diff. As expected, I still prefer my own definition. Properties and relationships are best summarized as laws. Note that while things that we think are laws may be disproven and therefore not laws, there are genuine laws that exist. I don't like the personification in "it seeks to". The note on the definition of "laws" may be out of place. If the distinction between classical and modern is no longer important, then perhaps it shouldn't be mentioned, and in its place describe the various sub-fields. –M^T 21:59, 10 October 2006 (UTC)

IMO, the distinction should still be mentioned for historical purposes - since it was an important distinction in the past and many articles may refer to it, it belongs somewhere in the opening statements. I still think the word "characterize" (or some reasonable facsimile thereof) needs to be in the first or second sentence, since that's ultimately what most physicists (indeed, most scientists) do. Finding the fundamental reasons for why things happens is all well and good, but even if a theory is wrong, it (can) provide a good mathematical model characterizing an interaction without ever explaining why it's so. I also disagree with the inclusion of "matter" and "energy" in the first sentence; it may sound a little too mumbo-jumbo-y to a casual reader and implies something related to QM, GR or ST (which obviously isn't true, but still...). Simply saying "the natural world" is far clearer and more general - technically everything revolves around the study of matter and energy, but most fields aren't concerned with the details of matter and energy in the implied sense. —Preceding unsigned comment added by Virogtheconq (talk • contribs)

In that case I agree on keeping the distinction. I'm a casual reader (layman in physics), and "matter and energy" is pretty clear to me. "Nature" on the other hand is absolutely ambiguous. All science concerns itself with the natural world. Physics distinguishes itself by focusing on ... well, plain old matter and energy. Those small and universal things that make up the bigger things. –M^T 00:03, 11 October 2006 (UTC)

Discusion continues below under the Discussion, continued heading. --MichaelMaggs 11:16, 11 October 2006 (UTC)

Structure

Yes, striving for a general definition will indeed take you down philosophical and metaphysical roads! That's not altogether a bad thing though. I agree that my definition is one extreme; thus, we should have many definitions: one for everyday use, one general, one specific, etc. You have struck at the heart of the issue when you say that there is no formally-agreed definition: many people define what physics is and its bounds of working validity subjectively. In fact, you may argue that the mating habits of King Penguins is indeed physics! So, let's sort out each of these definitions in turn. I would like to keep the general definition of physics for the sake of pedantry and the "rigourous way". I would also add the "particular definition" - i.e. the one that says, "yes, physics is actually a science". In fact, I only gave you half of my definition: I was going to add the latter half later on (since nobody uses a practical definition that speaks of the true laws of nature - these are not known!). So, lets first decide the type of definitions. I suggest:

Lay, easily understood definition - for the casual reader to have a general understanding of the topic.
General definition - one that is "rigourous".
Specific, or particular definition - a more useful, working definition than the general one.

We can discuss your suggested lead paragraph in more detail bit-by-bit once we have a clearer direction of where we are going. Krea 17:12, 10 October 2006 (UTC)

More editors welcome

It would be good to have a few more editors here. I have posted welcome notices to users who are on the Physics Project participant list.--MichaelMaggs 08:46, 11 October 2006 (UTC)

Discussion, continued

I've tried to pull the threads together, so far as I can, and I set out a revised proposal below. We ought I think to keep in these lead paragraphs the distinction between modern and classical physics, as they are common categories that readers will have often come across. The paragraph on laws is, I think, important to keep here as a lot of readers may well have heard the term law of physics with no understanding of what it means. I agree with M on using the terms matter and energy. For the reasons I've already stated the alternative 'Nature' or 'Natural World' are too broad as they don't in any way limit our understanding of what physics actually is (which we could perhaps think of a 'what physicists actually do'); they don't study King Penguins!

Physics is the science concerned with the properties of matter and energy, and the relationships between them. Physicists seek to characterize and describe the physical properties of the universe at the most fundamental level, normally by way of mathematical modelling of the behaviour of physical systems. Physics is therefore closely related to mathematics, which is the logical framework that allows for the precise formulation of these descriptions. The aim, however, is to go beyond describing physical phenomena, and to construct mathematical models or theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to support or refute the theory.

Some theories are of such significance that they are referred to as the laws of physics. Typically, these are physical principles that are believed to be common to all physical systems, or at least are of very general applicability. Some principles, such as Newton's laws of motion, are still generally called "laws" even though they are now known not to be of such universal applicability as was once thought. The word 'law' is a misnomer since even a law of physics could, in principle, be disproved by experiment. Other theories are more limited: they describe the behaviour of specific physical systems only, or are applicable only under certain circumstances.

Classical physics traditionally includes the fields of mechanics, optics, electricity, magnetism, acoustics and heat. The more recently discovered fields of general and special relativity are also usually placed within this category. Modern Physics is a term normally used to cover fields which rely on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics, solid state physics and condensed matter physics. Although this distinction can be commonly found in older writings, it is of limited current significance as quantum effects are now understood to be of importance even in fields previously considered purely classical.

Physics research is divided into two main branches: experimental physics and theoretical physics. Experimental physics focuses mainly on empirical research, and on the development and testing of theories against practical experiment. Theoretical physics is more closely related to mathematics, and involves generating and working through the mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available. Most theoretical physicists work on aspects of particle physics and related fields.

--MichaelMaggs 11:58, 11 October 2006 (UTC)

I really like the preceding paragraphs by MichaelMaggs. Here are a few comments:

I think it's important to say (near the comment on the more limited theories) that one of the major goals of physics is universal applicability, i.e., progress is made when you expand the range of validity of a single, unified understanding.
I wasn't aware that solid state physics and condensed matter physics were separate regimes. I think solid state is a subset of condensed matter but I'm not an expert in that area.
It might be dangerous to say that most theoretical physicists work on aspects of particle physics without backing it up with a demographic citation. There are a fair number of theorists in condensed matter, too, although they don't get as much press as the string theorists. I was going to suggest mentioning phenomenology here too, but decided against it since it's a bit too specific for an intro (and I think the theory/phenomenology/experiment distinction is mainly limited to particle physics). HEL 13:04, 11 October 2006 (UTC)

Thanks, HEL. Those are all useful comments and I think we should edit them in. --MichaelMaggs 13:58, 11 October 2006 (UTC)

Me too. This is a nice, solid, concrete definition. linas 04:22, 12 October 2006 (UTC)

Excuse me. MichaelMaggs, could we kindly stop and take everything in for a moment. We have 2 different viewpoints on the definition. You have objected that my definition is too general (I agree with that), whereas I object that yours is too narrow and specific. What is wrong with including both? Why not say, "physics is the study of this or that...", and then say, "we can have a more general definition of physics that says..."? Is it that you don't agree that my definition is useful (because it is too general)? I agree that it is not useful, but I still believe it should be at least stated because it is the only definition that is always true. I think the mathematically and philosophically minded members of this discussion would appreciate that. Thus, can we stop for a moment and outline what the structure of this section should be. Neither you and M, nor I should continue without a clarification of the issues at hand. Krea 13:29, 11 October 2006 (UTC)

Hi Krea. Yes, I'm more than happy to continue the discussions, but I must confess to having real problems understanding the thinking behind your definition. It seems to me - please correct me if I'm misinterpreting - that you are arguing that your definition is correct because it is broad enough to encompass all of physics. It is extremely broad, true, but to my way of thinking a definition should so far as is possible cover only the subject being defined, nothing more. To the extent that your definition covers things (such a biology) that cannot on any reasonable use of the word be considered to fall withing the scope of physics, it is wrong. You have agreed that your definition is in any event not useful, and I don't understand the argument that Wikipedia would be improved by having non-useful definitions added to it. --MichaelMaggs 13:55, 11 October 2006 (UTC)

Thanks for clarifying what is troubling you. You're partly correct, but you seem to have also partly misinterpreted my meaning. It's quite subtle, and it would be better if I could explain this in person, rather than through words, but I'll give it a go. Definitions, in a sense, can't be "correct" - they're definitions! All they can hope to be are consistent, and useful. When I formulated that definition, I didn't think: "in order to ensure that I encompass physics in my definition, I'll make it really general so that nobody could possibly argue that it is wrong". What I did was this: I just made any consistent definition of physics (not something contradictory), and then asked myself: is it useful to us in some way? My general definition is not useful in a practical sense, but I still argue that it is useful because it is required for aesthetic purposes (sorry for not saying this before, and so contradicting what I did say before). Let me explain.

When I formulate definitions, I would like them to be independent of the thing that they try to describe. For example, if we define physics as the study of particles (for example), then the definition is based on things that physics itself identified! That's a bit silly because, in a sense, it is circular: physics defined particles, and particles now define physics. This requirement is, of course, one of personal "aesthetics" (i.e., what makes a good definition?) - but many theorists, mathematical theorists and philosophers prefer things this way.

Many people, myself included, search for such definitions that satisfy this "aesthetic" property. The problem is that this also make the definition very general. Specifically, if we wish to keep this aesthetic quality, we must admit that everything is physics! Thats not too unreasonable: penguins are physical objects and they do interact via the laws of physics, so, in a way, they could be thought of as being under the bounds of physics (ignoring issues of consciousness - don't ask!).

Thus, you have to ask yourself what's more important, a defintion that correlates with what you feel physics is (and that means not including penguins!), or one that is "aesthetically nice". That's my only justification for including this definition: just because it has some favourable properties.

So, it's not completely useless, it's just not very practical. Thus, I would like to have both: one that gives you a feel for the subject (but has some undesirable properties), and one that is "nice" and "rigourous" (but not very practical, and gives you no everyday sense of the subject). If I haven't convinced you of the desirable properties of my general definition, please permit me to try harder! Krea 15:49, 11 October 2006 (UTC)

I must confess I'm not a philosopher, but a practical physicist. While I understand the desirability of having non-circular definitions, we do need something that make sense to the average reader, and which tells him or her something useful about the subject under discussion. On your own admission your wording implies that everything is physics, and furthermore that it gives you no everyday sense of the subject. The concept of "aesthetics", in the sense in which you use it, would need a lengthy exegesis which even if it were helpful would not, I feel, fit into this article. For that reason I'm against having two definitions. Also, as M has pointed out, it harms us to think of the first sentence as a definition in the strict sense. We should view it as a practical description of the remit of the subject.--MichaelMaggs 17:53, 11 October 2006 (UTC)

It need not be too lengthy. Of course, it should not be the first thing the reader reads! But I still think it should be there somewhere. Let me just say for the record that I don't like the idea of saying that the lead section be short: it needs to be a big as it needs to be. It must, however, be readable and well structured. Also, definitions on physics are personal - there is no written formal definition, and this should be said.

I would really like to look back on this when it is finished and be really pround of it: to think, "you won't find anything better than that on the internet", instead of thinking that it was compromised. Come on! Let's not take the easy route. Let's at least give it a go. Let's give it the "all out" treatment! What about this:

Start the article off really slowly - easy ideas, commonly understood phrases.
Then say that there is no formal definition: that many people have their own definitions of what physics is...
and then introduce some definitions that are more "desirable" in some ways.

If we can keep it well structured, it should be fine. I don't think we need to write essays: we can just say that the first definition is circular, and that avoiding this leads to this definition, and then point out some of the objections of this definition. Viola. That's not too bad is it? If it becomes long and difficult to follow, then I agree that the article would be better off without it, but I really don't think it will become so. What do you say? Besides, I can't let you experimentalists get the only say!! Krea 22:48, 11 October 2006 (UTC)

Putting my replies down here since I can't arse myself to properly find where they need to go.... Certainly the first sentence isn't the end-all be-all of a definition of the subject, but given as its the first thing the reader is going to see it will have the most impact. Given that we seem to be having difficulties agreeing on a definition, perhaps that ought to be addressed instead: something along the lines of how broad a field it is, and then trying to establish some definitions. I still object to the use of "matter and energy" as it implies something about the majority of subfields which really isn't true: in my experience, saying "matter and energy" to most average people will immediately provoke a comment about QM, ST or (more rarely these days) GR, which is really just a tiny fraction of the total population of physicists (though the only ones worth a darn to the media, apparently). Maybe I'm just splitting hairs, but that's what my experience has been, and I think it does the article a disservice to (unintentionally) lean it towards a particular field. Virogtheconq 00:54, 12 October 2006 (UTC)

"Physics is the science concerned with the properties of matter and energy, and the relationships between them." might also be stated

Physics is the science which began with inquiry on the nature of things, starting with atoms and the void, ranging to the motion of the planets, and extending to the cosmos and the microcosm.

--Ancheta Wis 03:48, 12 October 2006 (UTC)

I like Ancheta's idea too, of taking of from a historical view, although that actual sentence is awkwardly worded.

How about:

Physics is the science which began with inquiry on the nature of things, the properties of light and structure of matter, the motion of the planets, and extending to the fundamental forces that shape the cosmos and govern the motion of atoms and the very smallest particles in nature.

I dunno, it hard to write a good sentence. I also don't like the link to "on the nature of things", its too specific for the general definition. linas 04:40, 12 October 2006 (UTC)

Whoooah guys, calm down! We've got to sort out what we want to do first. There's this whole issues of multiple definitions. I'd personally like to say that lots of definitions are possible, each with their own merits and shortcomings. So far, there are 2: a simple one, and one that I suggested (it's somewhere above). I doubt anybody objects to the "simple definition", but does anybody else object to the one I suggested? Plus, does anybody want to add another defintion with reasons on why it is useful? Krea 11:46, 12 October 2006 (UTC)

Just to add my two cents: I prefer MichaelMaggs's lead-in above,

Physics is the branch of science concerned with the properties of matter and energy, and the relationships between them. It seeks to understand and describe the physical properties of the universe at the most fundamental level possible, normally by way of mathematical modelling of the behaviour of physical systems. (etc)

I have no problem with "matter and energy" in the first sentence; to me it seems to fit everything from fluid dynamics to vibrational solids to particle physics, but then I'm a particle person so I might not be hearing it the way others would. Virgotheconq, do you have another suggestion? The second sentence together with the first adds a lot of solidity and really clarifies the definition, in my opinion.

Krea's proposed definition (copied from above; please let me know if I didn't find the right one you were referring to!):

Physics is the body of, or method of obtaining, statements that assert the manner in which nature truly behaves.

I am not as happy with it because to me it feels kind of vague. Could we cut out the words "assert", "manner", and "truly"? Isn't this statement, rewritten in plain English, just Physics is the set of statements about the way nature behaves, and the method for finding them out? But this applies to all of science, and then we run into the problem of penguins. We may like to say "everything is physics", but everything is not physics. We can talk about the linkages, like biophysics etc, but that's the application of physics to biological systems, not fundamental physics research. (Oh, and I'm a theorist. :) HEL 12:26, 12 October 2006 (UTC)

I think I'm going to second this opinion. The intro suggested by MichaelMaggs is clear and to the point, and I believe that most physicists would identify with studying "the properties of matter and energy". A more general definition runs the risk of being too vague, and anyway: "the properties of matter and energy" should be general enough for anyone! O. Prytz 13:10, 12 October 2006 (UTC)

Having just endorsed it, I have to say I have a bit of a problem with physical properties of the universe. If I were studying, say, high-T_c superconductivity (an unsolved problem in theoretical physics!), that phrase wouldn't really cover me. How about universe and its contents? (Or maybe, physical world or material world?) I want to avoid using the word nature here, because while a physicist would probably say high-T_c superconductors were part of nature, a layperson wouldn't, because they are man-made. HEL 13:23, 12 October 2006 (UTC)

Okay, these suggestions are missing the point a little: I'm not looking for opinions on whether you like it or not. I argue that it is a useful definition (although, not in a practical sense - which is what has been already mentioned), and I want to know whether people disagree with this or not. Also, just a few remarks: the word truly is required because this leads to distinctions about the fact that we do not know the true laws of nature; the rest are, yes, probably superfluous. Furthermore, you cannot say, "but everything is not physics," because the truth of that statement depends upon your definition, which is what we are arguing for in the first place! It's like saying your definition is not true, because my definition says so!

Again, forget the specific content, all I want to know is if you agree to the idea behind this definition or not. Specifically, this definition tries to define physics independently of the objects that it itself defines - in effect, avoiding a circular definition. Having clear and understandable definitions is all good and well, but does not one of you also want a more "solid" definition? Krea 13:31, 12 October 2006 (UTC)

Krea, I appreciate your persistance, but I don't think I do want another definition which is more 'solid' (or 'aesthetic') according to the meanings that you're applying to those words. Any definition, however 'aesthetic', which implies that everything is physics, and which gives you no everyday sense of the subject is sufficiently content-free, in my view, to be excluded from this article. You have already argued long and hard on the main Physics talk page for your proposals from March to July 2006 and I'm afraid I'm no more convinced than were the other editors there. --MichaelMaggs 16:22, 12 October 2006 (UTC)

I'm aware of how hard I tried this summer, but I still cannot believe anybody would want to settle for such a sub-standard definition. And make no mistake, it is sub-standard; useful for the public undoubtably, but nevertheless a poor definition. I hoped that it could be supplemented with something more "solid", but alas, those who don't think "mathematically" seem to have the majority. So be it. Krea 16:43, 12 October 2006 (UTC)

Very few would understand a rigorous definition. Rigorous definitions exist, but are not mainstream physics. The positivists have some definitions, but no one pays attention. That has got to be significant. Possibly because no physical predictions have come out of these efforts? So no one pays attention? --Ancheta Wis 17:21, 12 October 2006 (UTC)

The world of language is, sadly, not as precise as the world of physics. You have not, and I suspect won't be able to, provide a definition of physics that is a) complete b) comprehensible c) short and well-formed. When you use the word "nature", you lose comprehension: penguins too are part of nature. Continue proposing, of course, if you wish. Just be attentive to what you lose when you gain. I think that the best way to handle it is to make it comprehensible, short, and well formed. Completeness down to detail can be left to the rest of the article. –M^T 08:55, 13 October 2006 (UTC)

"...and the relationships between them" seems like a waste alongside of "the properties of". Readers can guess that we're not excluding relationships. Do physicists sharply distinguish 'properties' and 'relationships'? I would use the word "behaviour" to cover all that, myself. "Concerned with the properties of matter and energy" is redundant to "concerned with matter and energy". Readers will know that it's the properties, or the behaviour, or the inter-relationships even if you omit those words. The real issue, if there is one, is what the form of the concern is not stated. That it's scientifically concerned with matter/energy is good, but perhaps being explicit about understanding/discovering/characterizing is better. "Universal" was brought up, which is a better word than "fundamental", for reasons more than political correctness. With this in mind, the definition:

Physics is the science concerned with the properties of matter and energy, and the relationships between them.

would be stripped (made cleaner/clearer) down to:

Physics is the science concerned with matter and energy.

which is fine, but I suggest:

Physics is the science concerned with the discovery and understanding of the universal laws which govern matter and energy.

I have the following bracketted commentary on the rest:

Physicists[worthy of linking] seek to characterize and describe the physical properties of the universe at the most fundamental level[this is all just a rehash of the above paragraph], normally by way of mathematical modelling of the behaviour of physical systems. Physics is therefore closely related to mathematics, which is the logical framework that allows for the precise formulation of these descriptions[we already state that physicists formulate/characterize/describe by way of this logical framework; this is redundant]. The aim, however, is to go beyond describing physical phenomena, and to construct mathematical models or theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to support or refute the theory[or should we stick to falsifiability?].

One important thing to keep in mind is that this article is not within the domain of physics, though it's about physics. Words like "nature" and "characterize" don't have the same rigid and useful meanings. –M^T 08:55, 13 October 2006 (UTC)

Sorry to respond so late, but my Internet connection only works about once a day for a variable amount of time, so I'm a little behind on the discussion.

I have no problem with "matter and energy" in the first sentence; to me it seems to fit everything from fluid dynamics to vibrational solids to particle physics, but then I'm a particle person so I might not be hearing it the way others would. Virgotheconq, do you have another suggestion? The second sentence together with the first adds a lot of solidity and really clarifies the definition, in my opinion. - Matter and energy are fine in a technical sense (ultimately every subfield uses energy to try to characterize matter behavior), but again, my concern is the general connotation of the terms. The casual reader coming to this specific article is influence by what those two words mean in the mass media, which is mostly modern physics: most of the people I went through undergrad with are far from those fields (as a clarifier, I come from an astrophysics, not cosmology, background, though only at the undergraduate level - I've since migrated to astronautics). While "matter and energy" may be the tools we use to characterize the behavior of whatever it is we're studying, it's not the ultimate purpose of the study in and of itself (with a few exceptions, of course).

I personally think "nature" and "characterize" are just fine. For the former term, HEL has an arguable point, but physics encompasses so many fields (geo, bio, chem, materials, etc.) that there's no way to capture them all without using some catchall, sorta indefinite term like that. For the latter term, I think characterization both within the physics domain and outside is rather cut and dry: I would argue the entire purpose of most sciences in general is to find a way to describe (characterize) phenomena we see around us (primarily; finding the root causes would be a close second). Mathematical characterization is still characterization, and ultimately mathematical models still can qualitatively characterize what is happening.

That being said, my estimation is that a more general, simple sentence (not even definition) needs to be used to open the article to describe how wonderfully varied/encompassing "physics" is (that variance probably being the cause of our disagreement), and as such cannot be fully articulated simply. I can give it a stab later today or tomorrow working off MichaelMagg's architecture (I generally like his opening but for the semantic arguments I've been making), but don't expect anything until tomorrow at the earliest. Virogtheconq 14:38, 13 October 2006 (UTC)

Again I stress that "nature" is not the right word. The things that physicists study are at the root of everything, yes, but 'everything' is not what they study. Ask the average person "which science studies nature?" - my bet is that they'll reply with "biology" or "zoology". Using that sort of definition will unnecessarily and disproportionally blur the edges of what physics is. –M^T 20:38, 13 October 2006 (UTC)

Before we let the King Penguin thread die, it is pertinent to note that according to the laws of physics, all of nature should be subject to the laws of physics. Thus living organisms are subject to gravitation, etc. --Ancheta Wis 21:58, 13 October 2006 (UTC)

You say that a system fundamentally operating under the laws of physics falls under physics - this is wrong. Maybe when we have computers that can, using a complete theory of everything, model, say... quasi-infinite environmental factors operating on a quasi-infinite set of penguins to determine average results, then we'll be able to say that physics covers the "natural world", that really biology and medicine and psychology and even chemistry fall truly and fully under physics. As it is now, physics covers the fundamental laws of the particles that make up the natural world, and has practically nothing to do with complex systems like penguins. Physics covers only one part of the natural world: the fundamental. Matter and energy. –M^T 04:52, 14 October 2006 (UTC)

M is quite right. Saying that "penguins are subject to the laws of physics" or, more broadly, "all of nature is subject to the laws of physics" actually tells us nothing about the actual range of scientific enquiry that can be carried out within the science that we call "Physics". Is a study of the mating habits of King Penguins research into Nature? Of course. Is it Physics? Absolutely not. --MichaelMaggs 08:36, 14 October 2006 (UTC)

Allow me a little story: as a result of Operation Paperclip one of my teachers, Kurt Lehovec, formulated the equations behind "The photovoltaic effect", Phys. Rev. 74, 463 (1948), #6; also #1, 3 and 5, from some rocks he found, sitting in his desk, at the United States Army Signal Corps in Camp Evans, New Jersey. Being curious, he managed to identify the rock as silicon carbide and published equations relating the emitted light from the rock under the influence of a current, and vice versa. Do you call that physics? I happen to do so. By the above reasoning, Lehovec was engaged in an esoteric form of electronic engineering, and indeed he is one of the founders of the integrated circuit industry. But I call him a physicist. That is not merely my POV; the editors of Physical Review thought so too. Or might the application to electronics be the only thing? No. It was brand-new. That makes it interesting to physics. --Ancheta Wis 11:08, 14 October 2006 (UTC)

Let's call it physics. He was doing physics, and this discovery through physics led to the field of electrical engineering. I don't really see the relevance, so I'll re-iterate. The word "nature" covers penguins, penguins aren't physics, so "nature" is too broad. You seem to say that penguins (and electrical engineering?) are physics. This is wrong. A physicist doesn't care about the penguin and how it behaves, he cares about the stuff that the penguin is made of, and how it behaves. "But the penguin's behaviour is dictated by its molecules" is true, but irrelevant: physics is incapable of predicting anything in terms of relatively massively complex systems like penguins. Or cells. Or (I've heard) even many chemical reactions. –M^T 12:37, 14 October 2006 (UTC)

I have no problem in calling that physics. It's a pretty clear investigation into some properties of matter and energy. But how would you deal with my 'mating habits' question?--MichaelMaggs 12:46, 14 October 2006 (UTC)

M, so that we not escalate, I use φυσική (phusiké): the subject of φυσική is matter, energy, etc. But φύσις (phúsis) is governed by fundamental law, to which it is subject (i.e. to which it obeys). Ilya Prigogine (whom I call a physicist) has made a start on your critique of the limitations of physics by introducing the concept of the 'thermodynamic branches' of 'systems far from equilibrium'. I admit, the subject has a ways to go. But it has gone beyond simple systems.

MichaelMaggs, life itself was shown to have a reasonable physical explanation with the discovery of the structure of DNA. One of its discoverers, Francis Crick (whom I call a physicist) cast off much of the essentialist baggage of life force or vis viva etc by requiring only a view of the structure, and nothing else. That was that physicist's POV. And the discovery was made in Lawrence Bragg's lab. Before we proceed, I respect your current precis, and am only worried about the essentialist cast of its first sentence. --Ancheta Wis 14:41, 14 October 2006 (UTC)

I'll add one more thing, and then I'll leave it up to the rest of you guys to sort this out: "all of nature is subject to the laws of physics" actually tells us nothing about the actual range of scientific enquiry that can be carried out within the science that we call "Physics". So what? I'm a stereotypical theorist: I genuinely don't care about the practicality of physics. Having a vague definition that admits all of nature is physics really does not cause me any concern (because ultimately, this is probably true). The fact that the understanding of physics is not yet at this level does not mean that we cannot define physics this way. This view is by no means untypical of many theorists and mathematical physicists. Why, then, should an experimentalist view prevail? Merely because there are more practically-minded people here who don't like that way of thinking. And that is the key word: like. These views are not wrong (they are just definitions after all), they are just being forced out by the majority. Krea 10:51, 14 October 2006 (UTC)

All of nature is not physics. Rather, all of the particles that make up nature are governed by the laws that physics studies. You're confusing component parts (matter and energy) with some whole (earthly biology, medicine, psychological systems, penguins, etc.) Physics studies the component parts, but not the wholes. –M^T 12:37, 14 October 2006 (UTC)

Krea, you seem to be using the word "definition" in the mathematical sense (let x=y), in which we can can never be wrong because we are defining things to be some particular way. But what we are discussing here is not a definition in that sense at all, it's a decription of the way in which the word "Physics" is applied in ordinary English usage. We're not addressing how the word might be used when our understanding of the universe reaches some as-yet unknown level: that's an issue for future editors, assuming the encyclopedia is still around then. This is a purely practical issue, and editors who take issue with you need make no apology for being practically-minded people. --MichaelMaggs 13:59, 14 October 2006 (UTC)

Ah, so much has been said about the definition of physics – here, and before this WIP page was set up. Here's what I have to add:

There is no reason to suppose that the term has one single proper definition.

The Shorter Oxford English Dictionary (SOED), and its big brother the OED, give two relevant definitions. Here are the two as they occur in SOED:

1 a Hist. Natural science in general, esp. the Aristotelian system of natural science. L15.

b The branch of science that deals with the nature and properties of matter and energy, in so far as they are not dealt with by chemistry or biology; the science whose subject-matter includes mechanics, heat, light and other radiation, sound, electricity, magnetism, and the structure of atoms. Also, the physical properties and phenomena of a thing. E18.

Now, Krea and I are among those who insist on respecting the first of these definitions. Others are vociferous about the second. In fact, I think there is a strong case for respecting both. Historically, physics started out as simply the science of nature. In coming to a broad and robust appreciation of the scope of physics, we should understand it that way. Then, of course, we can point out that in practice the term is used in SOED's second way: as excluding chemistry, biology, and all the other special sciences. There is no conflict here. Compare an uncertainty about the meaning of body. The word is used in two different senses in these two sentences:

His head was severed from his body.
His whole body was sunburned.

In the first case, the head is something separate from the body, yes? In the second case, it is assumed to be included as a part of the body, and we infer that it is sunburned along with the rest of the body. So it is with the word physics: two senses, which we should be able to accommodate easily in our definition. In one sense, physics includes chemistry, biology, and all the other "sciences of nature"; in another, it is all that is left of natural science after you remove the special sciences.

Another analogy, closer to the situation of physics. Consider medicine. It is, roughly, the applied science concerned with the health and disease of the body, yes? So, given that the teeth are a part of the body, medicine should be concerned with the health and disease of teeth, right? Well, yes and no. Conceptually and broadly, dentistry is a part of medicine, and the teeth are one of medicine's concerns. It is valuable to think that way about the scope of medicine, at first. But then, as a practical and historical fact, dentistry and teeth are considered separately.

It is for this sort of reason that I have stressed the need for a historically informed approach to introducing physics, and to reaching a useful definition. My concrete suggestion? Something like this, as my first draft:

Broadly, physics is the science of nature: the science concerned with describing the basic constituents of the natural world, and specifying the laws governing their behaviour, singly and in combination. In most current uses of the term, physics is understood as more limited: there are special sciences (chemistry, biology, psychology, etc.) which are treated as if they were autonomous and not as parts of physics. This exclusion of some complex features of nature is a matter of mere historical fact and mere practical convenience; it does not limit the original scope of physics as the universal science of nature.

That's how I see things, anyway. Such a definition would need further work, of course. But if we are to achieve consensus at all, we must in the end give both senses of the term their due. – Noetica 13:30, 14 October 2006 (UTC)

"Physics" used to mean something different and probably broader, yes. In fact the field as we know it today derived from what used to be called 'Natural Philosophy'. And that's consistent with the first definition in the SOED, which tags that meaning as Hist[orical]. By all means let's cover earlier meanings in the historical part of this article: it's very important. But the lead paragraphs ought to concentrate on the primary meaning of the word to a modern educated reader. Collins English Dictionary gives:

1. The branch of science concerned with the properties of matter and energy and the relationships between them.
2. Physical properties of behaviour: [eg] the physics of the electron
3. Archaic. Natural science or natural philosophy.

--MichaelMaggs 13:59, 14 October 2006 (UTC)

Michael, you say: "Physics" used to mean something different and probably broader, yes. But it isn't just a matter of some single meaning that it used to have, and some other objectively discoverable single meaning that it now has. Yes, SOED, OED, and Collins – and other sources too, no doubt – give the "universal" understanding as historical, or somehow not current. That's why we need to respect the more current, more limited, sense. But that's not the end of the story. The sorts of limitations that physics is subject to are a matter of historical accident and practical convenience, just as the limitation of medicine by the excision of dentistry is a matter of historical accident and practical convenience. There is nothing conceptually fundamental or inevitable about either of these excisions – as limiting physics or medicine. In the case of physics, there will be new areas that are excised, no doubt. Since we have to come up with a definition that is robust enough to give what is conceptually important about physics, and what is immune to historical and practical accident, we need to respect the first definition too. If I am making one central claim, it's that. The debate so far has failed to issue in reasons for our disagreements. I urge you and others to consider this pluralist solution. We ought to be concerned with the place occupied by the science of physics in all of human intellectual endeavour (past, present, future, and merely possible), not just with that part of it falling within its scope according to current fashions in demarcations among the sciences. Beyond all that, as far as much current philosophy is concerned, the original sense of the term physics is indeed the best one to take as primary; and philosophy has a strong claim in this domain of definition and settling of concepts. – Noetica 14:35, 14 October 2006 (UTC)

Thank you Noetica!! Physics is more than what we can currently apply it to: it is also an idea, a concept - one to acquire knowledge (of everything). Michael, I wasn't aware that, "...what we are discussing here is not a definition in that sense at all, it's a description of the way in which the word "Physics" is applied in ordinary English usage." Ahh. Then why call it a definition then? Indeed, in this case, "editors who take issue with you need make no apology for being practically-minded people." Also, I know we can never be wrong with definitions - I have said so on several occasions. I'm not particularly pleased about this situation: I thought it was fairly obvious that under the heading "definition", we would be discussing definitions. As Michael has said, I have tried for too long to convince people that this DEFINITION was useful, and if people can't even grasp that it was a definition then why am I bothering? Krea 15:44, 14 October 2006 (UTC)

Krea, Surely it's been the rule since Samuel Johnson that dictionary definitions (which is essentially what we are talking about here) are descriptive not prescriptive? I imagine we can all agree that the dictionary definition (or description) has varied over the years, and that that neeeds to be reflected in the article. But there is simply no way to specify/define a word or a science in the strict mathematical sense without doing violence to the language. In the mathematical or prescriptive sense you can define physics as anything you wish it to be, but that doesn't make it so. All you've done is to re-define one word as another, as per Humpty Dumpty: "When I use a word ... it means just what I choose it to mean - neither more nor less." There is no "real", "truer", "deeper", "more meaningful", "aesthetic" or whatever sense in current English usage than the practical one which is used day by day. If you want to discuss how we should best integrate historic meanings, fine, but failing that it's pretty clear that we're not going to agree on this.--MichaelMaggs 18:08, 14 October 2006 (UTC)

Show me how physics can predict and describe anything useful about a complex system like a penguin, as biology could. Under "nature" fall both complex systems, and constituent parts like matter and energy. Physics studies the latter. How many physicists are attempting to make physics cover the former also? –M^T 20:24, 14 October 2006 (UTC)

Michael, you write as follows:

There is no "real", "truer", "deeper", "more meaningful", "aesthetic" or whatever sense in current English usage than the practical one which is used day by day.

I disagree. Sure, people use the term physics in an everyday fashion for everyday purposes. Most of most people's everyday purposes are, of course, immediate and practical. One such purpose is to identify physicists, and their concerns, separately from chemists, biologists, planet scientists, with their various concerns. Fine. Same with medicine and dentistry!

But there is indeed a "deeper" meaning for the term physics, and it too is a current sense because it is perennial sense. A dictionary, since it is adapted for everyday purposes, may reasonably give this deeper meaning less prominence. But any respectable encyclopaedia will treat the matter more comprehensively and philosophically. Consider this from the introductory material in Physics in Encarta (though please don't take this as a general endorsement of Encarta). I add emphasis in bold:

II SCOPE OF PHYSICS

Physics is closely related to the other natural sciences and, in a sense, encompasses them. Chemistry, for example, deals with the interaction of atoms to form molecules; much of modern geology is largely a study of the physics of the Earth and is known as geophysics; and astronomy deals with the physics of the stars and outer space. Even living systems are made up of fundamental particles and, as studied in biophysics and biochemistry, they follow the same types of laws as the simpler particles traditionally studied by a physicist.

And further along in the same article:

Even into the 19th century a physicist was often also a mathematician, philosopher, chemist, biologist, or engineer. Today the field has grown to such an extent that with few exceptions modern physicists have to limit their attention to one or two branches of the science. Once the fundamental aspects of a new field are discovered and understood, they become of interest to engineers and other applied scientists. The 19th-century discoveries in electricity and magnetism, for example, are now the province of electrical and communication engineers; the properties of matter discovered at the beginning of the 20th century have been applied in electronics; and the discoveries of nuclear physics, most of them not yet 40 years old, have passed into the hands of nuclear engineers for applications to peaceful or military uses.

Now, the assertion that I mark in bold here is ill-phrased, and there are problems of logic and expression in the whole passage. But the central message is clear: a physicist was a generalist, and physics was all-encompassing; but because the science had grown more complex, with so many powerful discoveries expanding its horizons, it was a practical necessity that parts of it be taken over by various special sciences. This brings about the everyday sense of the term: physics as the "remnant" of fundamental natural science that is left, after those specialist excisions.

That's part of the story. To show another part, let's take chemistry as an example. It might have some notional claim to being the result of the "first cut" applied to the body of physics. But no: it has for historical reasons always developed separately. To speak approximately but with sufficient truth and relevance, it developed not from a Greek source and through a continuous "Western" route, but along a Middle Eastern path. It therefore acquired its own separate baggage of terms, methods, and concepts. Should this accident of circumstance settle how relations between physics and chemistry are best thought about? No! Just about all chemists and physicists acknowledge that the laws discovered in particle physics and quantum physics ultimately and completely determine the truths of chemistry. In an important sense, chemistry is reducible to physics: and, in another equally important sense, this amounts to chemistry being a part of physics, as Encarta (bless it) allows. Britannica, while general stressing the modern "excised" sense of the term physics, also acknowledges this "nesting" of chemistry within physics. I have only an old hardcopy version to hand right now, but it offers this in the article Nature, Philosophy of, in the section headed Philosophy of Physics:

Inasmuch as the binding forces of chemistry can now, at least in principle, be reduced to the well-known laws of physics, or calculated from quantum mechanics,[...], chemistry can henceforth be considered as a part of physics in theory if not in practice.

"At least in principle". That, if it's accepted, is enough to justify our including in our definition the broad, idealised, and robust conception of physics as the general, all-encompassing science of nature – alongside the more restrictive and practical sense, of course. I have seen no good argument here against having both elements in our definition; and it is most unlikely that there will be any consensus until such ecumenism is accepted. – Noetica 00:27, 15 October 2006 (UTC)

Physics includes those aspects of the other sciences and the things they study that are not unique to them and are not philosophy or mathematics. (Statistics seems to be a minor problem here.) How about "The system of underlying principles of the world" This is general and it implies the interconnections that are so hard for beginners to see. David R. Ingham 00:47, 15 October 2006 (UTC)

Physics can't predict and describe anything useful about a complex system like a penguin, as biology could. Yes, principles of physics can be applied by other sciences, just as math can be applied to them. But physics does not encompass the other sciences. Physics is absolutely useless in describing penguin behaviour, and I'm not talking about "gravity pulls the matter that penguins are composed of downwards". That's why we have biology etc., because physics just doesn't cut it when it comes to complex systems. It's as if some of you think that in understanding physics we'll understand everything. That's like saying that if we understand each word that a book uses, we'll understand the book. Science tries to understand nature. Physics tries to understand the fundamental components; things like matter and energy. –M^T 06:39, 15 October 2006 (UTC)

M, I will focus on this sentence of yours: Physics can't predict and describe anything useful about a complex system like a penguin, as biology could. You appear not to have absorbed what I have laid out above. That's not too heinous a crime! But I put it to you that what I have said – in detail and at length – opens up a way forward as we strive for a widely acceptable definition. Let me deal with your sentence in the light of the distinction I want to make.

Physics has two senses, I say. Let's call the physics that is all-encompassing broadphysics. Broadphysics includes all of the special sciences: chemistry, biology, planetary science, etc. And let's call the physics that excludes those special sciences narrowphysics. Narrowphysics is the remnant after specialised areas, mostly dealing with large and complex systems, have been cut away. Now, even if you don't like the distinction I make (and which some encyclopedias tentatively make, as we have seen), you will have to admit that it is an intelligible distinction. OK?

Now I ask you: what do you mean by physics in your sentence?

If you mean broadphysics, then the sentence is plainly in error. Broadphysics includes biology; so if biology predicts and describes facts about penguins, so does physics!

If on the other hand you mean narrowphysics, then the sentence is closer to being acceptable. Narrowphysical notions (like momentum, kinetic energy, electric charge, and so on – to restrict ourselves to classical narrowphysics) will have limited application when we try to give an account of penguins. But so what? Narrowphysics is simply the remnant of theory that is left after biology and the other special sciences are removed, and given subject matter, theoretical resources, and methods of their own. We can all agree!

If you mean neither broadphysics nor narrowphysics, please tell us what you do mean.

Narrowphysics is still strongly connected with the special sciences, of course. We can say that these special sciences are reducible to narrowphysics (however hard or impracticable such a reduction might be). Or we can be more modern, and speak of supervenience. The facts and laws of biology supervene of the facts of narrowphysics; that is say, it is impossible for there to be a change or a difference in the biological state of affairs without some change or difference in the narrowphysical state of affairs. – Noetica 07:54, 15 October 2006 (UTC)

Adding to what Noetica has said, we can indeed define physics in two ways. The first way is defining it to be the study of things, and the second as the set of laws of things (where I will leave what these "things" are dependent on how one chooses to make their definitions). I think that there is disagreement between us, M, because you talk of the former, and we of the latter. If we define physics to be the study of things that we, physically, "know well", then it is naturally restricitive (and arbitrarily so) and it is precisely Noetica's "narrowphysics". We can also define physics, however, as the set of laws of all things that we believe will ultimately come under the scope of physics. This is Noetica's "broadphysics". Some of these laws are unknown to us now, but that doesn't stop us making such a definition.

The "penguin definition" (the one I suggested), as I will now call it, was an attempt at a defintion based on the set of laws of "things". I still do not understand either of your, Michael and M, criticisms of it. When you said "penguins are not physics", you were taking the first sense of the word physics (that it is the study of things) from one definition, and applying it to the alternative sense (that it is a set of laws) from an alternative definition. This is obviously wrong to do. Within each definition, the description is sound (and, if I may go further, correlates well with what people think physics is). Start to mix concepts from different definitions, and you will certainly engender a long and pointless debate! I think that this is what has happened - right? Krea 13:47, 15 October 2006 (UTC)

Yes, we are indeed talking about different things, and if we can perhaps all identify what we mean, and agree how to refer to them, we may be able to move forward. Can I tentatively expand on the broadphysics and narrowphysics concepts and include some others that have also been discussed:

1. The study-based definition/decription

the type of scientific investigations that can be carried out, today, under the banner of the science of that name (based on the way in which the word is used in common English parlance, both by Physicsists themselves and by educated non-specialists).

For example: Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy.

2. The rules-based definition/decription

The set of physical laws which many (probably most) physicists believe underpins the fundamental workings of the physical universe, knowledge of which is at present very incomplete but which may in the future become better understood, thereby allowing a broader range of phenomena to be mathematically described.

For example: Physics is the set of univeral laws which define, at the most fundamental level possible, the behaviour of the physical universe.

3. The everything definition/decription

The physical universe itself, being subject to those univeral laws.

4. The historical definition/decription

The older sense of Natural Philosophy.

Probably (but please correct me if I'm wrong), 1. is what Noetica refers to as narrowphysics and 2. is what he refers to as broadphysics.

Now, it seems obvious to me (but others clearly disagree) that a science is properly defined by the type of investigation carried out (definition 1). The physical laws (definition 2) are the output of those investigations, while the universe (definition 3) is their subject. The historical definition 4 appears to be non-contentous.

Are we able at least to agree on these four classes, or something along those lines, and that all are worthy of mention in the article? If so then we are moving along, and we simply (ha ha!) need to agree on how best to elucidate these concepts for the reader. --MichaelMaggs 15:04, 15 October 2006 (UTC)

Progress!!!

1. The study-based definition/description

the type of scientific investigations that can be carried out, today, under the banner of the science of that name (based on the way in which the word is used in common English parlance, both by Physicsists themselves and by educated non-specialists).

For example: Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy.

2. The rules-based definition/description

The set of physical laws which many (probably most) physicists believe underpins the fundamental workings of the physical universe, knowledge of which is at present very incomplete but which may in the future become better understood, thereby allowing a broader range of phenomena to be mathematically described.

For example: Physics is the set of univeral laws which define, at the most fundamental level possible, the behaviour of the physical universe.

3. The everything definition/description

The physical universe itself, being subject to those univeral laws.

4. The historical definition/description

The older sense of Natural Philosophy.

[Big sigh of relief] Ahh, the sweet taste of progress! Anyway, yes, I think 1 is "narrowphysics" and 2 is "broadphysics" (but we'd have to ask Noetica to be sure!).

You say that, "physics is properly defined as...". Well, I personally think this is just one's own preference. I regard physics as being defined as 2 and that that leads to 1. But, I can certainly see the case for the alternative view: to which concepts we choose to identify the word physics is a reflection of our own character. For example, my mind thinks that 2 is a "better" definition because 2 is more "fundamental". Such arguments are, of course, complete rubbish. I don't want to go down the road of, "this definition is better than that one because...". A discussion of each definitions shortcomings would be nice though (but where to put this?).

I'm happy with ideas behind 1, 2, and 4, but can I check if I understand the meaning of 3? Does it mean to say that, "one definition of physics is the universe itself (and not of its laws)," or that it is, "the set of all laws (as per definition 2) and the universe itself too"? Krea 15:52, 15 October 2006 (UTC)

Definition 3 was my attempt to reflect what you said above, in this quote: Specifically, if we wish to keep this aesthetic quality, we must admit that everything is physics! Thats not too unreasonable: penguins are physical objects and they do interact via the laws of physics, so, in a way, they could be thought of as being under the bounds of physics (ignoring issues of consciousness - don't ask!). But if you actually meant 2, we could simplify things further and get rid of 3.--MichaelMaggs 19:40, 15 October 2006 (UTC)

I propose striking 3 to preserve a distinction between subject and object. --Ancheta Wis 20:03, 15 October 2006 (UTC) Note: Dbuckner has just rewritten the article on Definition. There has been progress on several fronts. 20:09, 15 October 2006 (UTC)

It may be helpful to follow the guidelines in Definition#Rules_for_definition when formulating the first section of this article. --Ancheta Wis 08:49, 18 October 2006 (UTC) And perhaps Fallacies of definition will be useful also. 08:49, 18 October 2006 (UTC)

I meant that quote to fall under definition 2. I think that when the time comes to sort out the details of the definitions, definition 2 will implicitly consume the ideas of definition 3. Anyway, I say strike 3 too. Krea 21:22, 15 October 2006 (UTC)

Yes, I'm for the "narrowphysics" definition. What you call "broadphysics", I call "science". A science is not just a body of knowledge. It's a study. And it surely isn't a set of laws, but a description/understanding/way of discovering those laws. Now, even if this article was about a set of as-yet-unknown laws that governed everything at some underlying point, it would still be improper to say that they govern nature, because most people wouldn't understand what that means. "Nature" brings to mind green forests, singing birds, lions tearing apart zebras, and not... what? "everything"? Even "the natural world" is wrong, because it's not like physics exludes the artificial. Perhaps "Physics is the science concerned with the discovery and characterization of the universal laws which govern stuff that isn't made up"? I can agree with that, but I don't quite support making it the definition. –M^T 22:58, 15 October 2006 (UTC)

Of course, the word "nature", or whatever else is used, will also need to be defined clearly (hopefully!). Bear in mind that this is not a popularity contest. You say that you, "...don't quite support making it the definition." Why? Just because you don't like it? That's not good enough. Also, it will not be the definition. It will be one particular definition that a significant number of people "like". If you call definition 2 "science" - good for you. What difference does that make? Indeed, since definition 2 essentially says that everything is physics, then all the sciences are really just subsets of physics - and the only science is physics. Remember, I'm not saying that this view is "correct", it's just a definition that some people subscribe too. Essentially, yes, details will need to be sorted out; and, I don't care if you, or anybody else, don't like any particular definition, unfortunately, because that is not sufficient for its removal. Krea 13:19, 16 October 2006 (UTC)

I "dislike" it because it's not good, or wrong. You seem to be accusing me of randomly throwing my whims about - please stop that. I'm offering what I think are very valid arguments to support my case. My reason for not supporting my definition was that "stuff that isn't made up" isn't very eloquent. | All sciences are not subsets of physics. Just because behaviour in a complex system studied by science X is ultimately caused by the interactions of things studied by physics, this does not mean that science X is a subset of physics. But before we get into that, I disagree that this article is about a set of as-yet-unknown laws that govern everything at some underlying point. It's about the study of those laws. Definition 1, not definition 2. | "Nature"'s connotative associations aren't the only problem, so taking a few sentances of the lead to define nature probably isn't a means to consensus. –M^T 22:15, 16 October 2006 (UTC)

Sorry. I don't understand what you mean when you say it is "wrong". It's a definition - how can it be wrong (besides contradictions)? Also, you keep saying that all sciences are not subsets of physics. Just so that we are not arguing pointlessly, can you make that statement as pedantic as possible (defining everything and stating all assumptions as best you can). It's late, and I'm pretty tired, but, doesn't "ultimate cause of" mean that things are subsets of physics? Again, reply to this question as pedantically as possible please. Before all of this, however, you want to discuss this "set of laws" thing: ok. Do you mean to say that physics is only a "study of things...", and not a "set of laws..."; or is it this "not-yet-known laws" business that irks you? Krea 23:24, 16 October 2006 (UTC)

Wrong means that the definition doesn't fit the term. | There are two senses to the word "physics", and they're reflected in the above definitions. These two senses are absolutely distinct[1], there's no point in arguing that one is a better way to describe "physics" than the other - which definition is more suitable to "physics" - because "physics" refers to two different things. We need to figure out which of the two this article will be talking about, the actual (unknown) laws, or the study of those laws? I say the study. | If you're still interested in preemptively discussing why biology isn't a subset of physics, leave a note on my talk page. –M^T 00:30, 17 October 2006 (UTC)

I have to admit that that I'm pretty tired of following this discussion. What we want is a complete reworking of the whole article, and we're still not done with the intro. Anyway, I thought I should contribute at least a little. So here we go. I want to define physics as Science. In my mind this means that we need to be able to make (quantitative and testable) predictions about the systems we are studying. We are genereally not able to make such predictions about many biological and chemical systems using the "laws of physics". Therefore, these areas are not subjects of the Science called "physics". Whether or not we will be able to make such predictions at some point in the furture is not a discussion I want to appear early in the article. To me it seems that my view is most accurately described by definition 1 given above

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy.

That's my opinion anyway :) O. Prytz 02:03, 17 October 2006 (UTC)

I imagine that the article will be about both the laws themselves, and their study: why limit yourself to only one? I'm sorry, but I'm not interested in "preemptively discussing why biology isn't a subset of physics". That's merely your definition of physics. Mine is different. So, what is there to talk about? It would be as pointless as a discussion on why God exists.

The fact that we are stuck at the intro is a good sign. This, and maybe the next section, will constitute the bulk of the ideas and concepts in the article. The rest will just be book-keeping. O. Prytz, I'm sorry, but, as you say, that's not much of a contribution. You like definition 1. Great. What's your point?

I'm sorry if my posts seem a little harsh, but this is not a popularity contest (or at least it shouldn't be).

M has realised one of the main issues: we can define physics as a study, or a set of rules: I doubt there's much controversy in that. But, there is a more pressing issue: one of accuracy. Let me state, again, that I'm happy to have a defintion, like the one O. Prytz suggested, right at the start just to give people a feel for the subject. But, I contend that that definition is poor. Consider: I study the Lagrangians of certain scalar fields; therefore, by that definition, I am not a physicist. Am I actually a physicist? Most people would say yes. Ergo, that definition is "wrong". If you want a more meaningful and accurate definition you're going to have to think and try a lot harder. Of course, I now wonder if the bulk of the editors here even want this. Krea 10:20, 17 October 2006 (UTC)

You need to give more consideration to the types of arguments you use. "You are dispensing opinion and pandering to popularity" is not a proper response. "That's just your definition, this is mine, there's nothing to talk about here" is not a proper response. "[You disagree with me and have provided valid reasoning]. Great. So what? What's your point?" is not a proper response. O. Prytz said "We are genereally not able to make such predictions about many biological and chemical systems using the 'laws of physics'. Therefore, these areas are not subjects of the Science called 'physics'", do you have a response to this?

I don't know what your exact objection to the definition is. Do you object because you think that we should be talking about the laws of physics? Or because "matter and energy" does not cover your field of study? Here's what an article on the laws of physics (definition 2) would look like:

#REDIRECT Physical law (or List of laws in science)

Now, as for "matter and energy" - it's the best we have. It may not be exact, but the meaning is perfectly clear. Perhaps "matter, energy, and fields/forces" is better? You suggested "nature" as a better term. The objection was that all sciences studied nature, the definition told us nothing. The response was "Exactly. They are all subsets of physics". This is wrong. For biological study (biology) to be a subset of physical study (physics), physics must be capable of "handling" (predicting, explaining) penguins as well as biology could, and biology must be composed entirely of physics - all 'laws of biology' must be laws of physics. This isn't the case. "Nature" is too broad a term for a science that is, yes, foundational, but not really all that broad. What do you propose the definition should be, with all this in mind? –M^T 21:43, 17 October 2006 (UTC)

It might help to use an analogy from navigation. Imagine the science of physics to be a sailing ship. The steersman has set a course from the points of the compass and is expecting, in the distance, at some time in the future, for the sailor at watch to sight land (remember, the ship is not at landfall, yet). The analogy is steersman<=>scientific researcher, course or bearing <=>scientific prediction, land<=>scientific corroboration and ship<=>the known laws of physics. True, the ship has not reached land, but that does not mean the goal cannot be reached, and that the ship cannot gain great wealth for the enterprise. --Ancheta Wis 22:05, 17 October 2006 (UTC)

Well, land would be the true laws of physics; the ship would be the means by which we get to the land: the scientific method of physics; the steersman's knowledge of navigating those tricky waters near the destination would be experience and study. But I don't think that this analogy is very useful, as it stands, anyway. Yes, hypothetically we can reach the goal of understanding the laws of physics. But right now, physicists are somewhere on the way to the peninsula of physics, whose spewing volcano is the ultimate cause of all the other lands (and the trees and animals that now inhabit them). Maybe the goal of some physicists is to hack slowly through the jungle of complexity that lies between physics and an understanding of biology, or psychology. Maybe. But that doesn't reflect what physics is now. You're describing the peninsula, or the entire continent - the goal - but not the boat and its current position. Perhaps you want to mention that physics is "ultimately concerned with ~~conquering the entire continent~~ understanding everything". And I'll ask you to cite that. And, personally, I don't think that understanding each of the 10^n molecules that make up a penguin will bring you any closer to understanding that penguin, as if sifting through the volcanic earth will tell you even a fraction of anything about the trees that sprout out of it elsewhere. Though surely people on the other ships will learn much of piloting from your exploits. –M^T 05:18, 18 October 2006 (UTC)

Using Ancheta Wis' analogy, the problem is this: a sailor sets off on his voyage with the aim of finding some unknown land. After a long time searching, he finds no land, but lots of clues (seagulls, floating branches - whatever). Now, how do we now describe the sailor? What is he? We can now define him to be some guy who analyses ocean debris - that's perfectly true. But don't forget why he set out in the first place: he can also be defined to be a person who seeks to find new lands. Your definition of physics, that talks of details such as energy, forces, matter, fileds etc. is the first definition. But, physics is more than that: its ultimate aim is to describe and understand everything (even if the only thing it may ultimately be able to say about some things is that nothing else may be understood) irrespective of what it finds on the way there; and it is this that leads me to formulate a "broader" definition. Fair enough, physics can't say much about biology now, but all physicists (I conject) believe that the ultimate aim of physics is to describe everything. If they believe this, then what is the problem in making a definition that states this? Krea 22:57, 17 October 2006 (UTC)

Cite "the goal of physics is to understand everything". Once you do learn everything of physics, how on earth do you expect that to tell you anything about biology? You're tunneling downwards towards simplicity, complexity is in the opposite direction. The simplicity that you'll find will expand exponentially as you move upwards towards penguins. How many molecules is a penguin made up of? How many "strings"? I think that it's a ridiculous claim to say that physics, with any practicality, will explain penguins. But anyway, that's not for me to say. Cite a scientific consensus that through physics we'll understand psychology. –M^T 05:18, 18 October 2006 (UTC)

Also, let me apologise to O. Prytz (my comments do appear to be quite harsh). My reply to, "We are genereally not able to make such predictions about many biological and chemical systems using the 'laws of physics'. Therefore, these areas are not subjects of the Science called 'physics'," is this: The fact that you say biology/chemistry is not physics is true under your definition of physics. You cannot then use that to justify why your definition is correct! It's like saying, "hats are not shoes because people do not put hats on feet." What was not said was that this is only true when you define shoes to be "things you put on feet". I could equally well define shoes to be "things you put on feet, or hats", in which case the original statement fails. The real argument is whether these various definitions correlate with what people believe shoes to be. Back to physics, people believe it to be the search for all knowledge (including biological); so, I conject, my "penguin argument" is valid.

It seems we actually do disagree on what physics really is. As I understand your arguments, you want physics to be something defined (as in a rigorous philosophical definition) in terms of things outside the domain of physics. Furthermore, you want this definition to have as a consequence that all of nature is inside the domain of physics. My objection is that if this were the case, we could no longer view physics as a Science (I'm capitalizing on purpose), or at least that all textbooks in e.g. biochemistry would have to be categorized as physics. None of these options are acceptable to me. A rebuttal of my objection might be something like: "but it's only a matter of time before physics is able to handle these things" and that I'm choosing an arbitrary point in time (today) to define physics. However, in my view, defining physics to contain all of nature is similar to defining Columbus as the discoverer of America, before he set sail from Europe. Furthermore, following your prescription, I'm afraid that we (at best) could only end up with one Science which would have to include all the Natural Sciences. I doubt that it would be recognizable as physics any more.

Physicists may or may not be able to discover the most fundamental theory of everything. But even if they do, saying that this theory explains all of nature is a long shot. I do not believe that it will ever be possible to work from these first-principles to describe all of nature (and by describe I mean deduce quantitative and testable predictions, because physics is a Science). In fact, if you want to describe the whole universe with these first principles, you would probably need a computer with the information handling capacity of... well... the Universe. This comes very close to my definition of impossible.

My view of physics is that it is messy and illogically defined, and probably circulatory in the sense that it is defined by what it studies. Just to finish off, I'd like to reiterate that I feel the "matter and energy" definition pretty much describes what physics is. I believe this should be the goal of an encyclopedia entry, and not an all-inclusive idealized definition which may or may not be logically sound. O. Prytz 13:31, 18 October 2006 (UTC)

My exact problem with the matter/energy definition is not specifically matter and energy themselves, but this: physics is not ultimately about matter and energy. These are just things that have been discovered along the way of the ultimate search for "truth". Thus, why only define physics in terms of the "details" and not the ultimate raison d'etre? Krea 23:27, 17 October 2006 (UTC)

Well, as I've implied, that's pretty lofty of you to think so. That seems to be the goal of science. Physics sounds like an arrogant brat, yelling about how it can do everything its brothers and sisters can, and prolly better too! (Nah, not yet, but when it grows up a bit more, it'll show 'em...) I strongly doubt that most people will agree that physics has any genuine shot at explaining everything. Let's stick to what most of the practical work in physics is focused on: matter and energy. –M^T 05:18, 18 October 2006 (UTC)

Einstein noted that the particle was not a fundamental concept; thus matter is not fundamental in this view, as particles have been created and destroyed. Matter can be created and destroyed.

Maxwell (1876) once wrote a popularization of physics, Matter and Motion, in which he states "Physical Science is that department of knowledge which relates to the order of nature, or in other words to the regular succession of events." - (page one ), ISBN 1-57392-989-1.

--Ancheta Wis 08:49, 18 October 2006 (UTC)

M, you don't seem to have a good grasp of physics. To say, "Once you do learn everything of physics, how on earth do you expect that to tell you anything about biology?" boggles the mind. Once the principles are known, the outcomes become mere application. (Note that these ideas are subtle, and there is more to it than what I have said, but that doesn't change what I have said beyond what is reasonable.)

No, Krea, what is mind boggling here is that you seem to think that applying the 'laws of physics' to complex systems is a matter of "mere application". Furthermore, you do not seem to grasp how important this "mere application" is if we want physics to be Science, and not just some collection of qualitative statements. O. Prytz 13:51, 18 October 2006 (UTC)

"You're tunneling downwards towards simplicity, complexity is in the opposite direction." indicates a fundamental misunderstanding: "simplicity" applies to concepts, and "complexity" applies to outcomes. They do not apply to the same thing; therefore, it is wrong to infer that physics and biology are going in opposite directions. Special Relativity was constructed from two beautifully simple postulates. The consequences of these concepts can be, however, far from simple. QM is similarly built from simple postulates (arguably not as beautiful as the SR postulates though) and look at how complicated and complex some quantum phenomena are.

"I strongly doubt that most people will agree that physics has any genuine shot at explaining everything." Let me weaken the statement "everything" to be everything excluding the Universe itself and anything beyond that, and perhaps consciousness. Now, if you ask the physicists who are contributing here if they think physics has a shot at knowing (this weaker) everything, I think you'll be disappointed. Many great physicists have stated that they believe physics' true domain is all of nature. In fact, this arrogance of physics is perhaps one of the reasons that attracts us to the subject. We can take a quick poll if you like just to see where we all stand on this issue? Krea 13:32, 18 October 2006 (UTC)

Folks, please, this argument is getting silly. I commented above that I think it's important to say that one of the major goals of physics is universal applicability, i.e., progress is made when you expand the range of validity of a single, unified understanding. I think we would all agree that the fundamental physical laws that apply to particles in a semiconductor also apply to particles in a penguin -- right? The understanding is that physics underlies everything, not that physics can predict everything (with today's computational power, at least!). Physics has branches that merge into other disciplines -- e.g., biophysics -- that are making those steps up the ladder of complexity. We already understand perfectly well all of the physical laws that underlie all of biology: they are just Maxwell's equations, Newton's equations, and Schroedinger's equation. Working upward to apply them and make useful predictions is the challenge: while you're still in contact with those physical laws, it's physics (or biophysics); when you switch to an understanding based on larger chunks of matter and empirical rules not derived from physics, then it becomes biology.

I think it's also pointless to try for a philosophical definition that doesn't rely on the definitions that come out of physics itself. I mean, biology is the study of living things, right?-- but the definition of what's a living thing falls under the realm of biology! We are dealing with language here, not math, and we are not genuinely defining physics but rather trying to describe in a concise way what physics is.

I'm not sure what Ancheta Wis is getting at with the comment about matter not being fundamental; I thought the possibility of creating or annihilating matter was implicitly taken into account when we wrote matter and energy. In fact, as a particle physicist I would interpret matter and energy as a euphemism for fields and their interactions, which is about as fundamental as it gets -- the PR buzzwords of particle physics in the past five years have been "the study of matter, energy, space, and time" (see, e.g, the ILC consensus document from 2003 (pdf)). Going down to lower energies - condensed matter, fluids, etc - "matter and energy" still describes the building blocks. HEL 14:57, 18 October 2006 (UTC)

I don't think it's pointless to try to make a "philosophical" definition. In fact, O. Prytz has made some very intelligent remarks above, so let me copy them out here just in case anybody misses them:

It seems we actually do disagree on what physics really is. As I understand your arguments, you want physics to be something defined (as in a rigorous philosophical definition) in terms of things outside the domain of physics. Furthermore, you want this definition to have as a consequence that all of nature is inside the domain of physics. My objection is that if this were the case, we could no longer view physics as a Science (I'm capitalizing on purpose), or at least that all textbooks in e.g. biochemistry would have to be categorized as physics. None of these options are acceptable to me. A rebuttal of my objection might be something like: "but it's only a matter of time before physics is able to handle these things" and that I'm choosing an arbitrary point in time (today) to define physics. However, in my view, defining physics to contain all of nature is similar to defining Columbus as the discoverer of America, before he set sail from Europe. Furthermore, following your prescription, I'm afraid that we (at best) could only end up with one Science which would have to include all the Natural Sciences. I doubt that it would be recognizable as physics any more.

Physicists may or may not be able to discover the most fundamental theory of everything. But even if they do, saying that this theory explains all of nature is a long shot. I do not believe that it will ever be possible to work from these first-principles to describe all of nature (and by describe I mean deduce quantitative and testable predictions, because physics is a Science). In fact, if you want to describe the whole universe with these first principles, you would probably need a computer with the information handling capacity of... well... the Universe. This comes very close to my definition of impossible.

My view of physics is that it is messy and illogically defined, and probably circulatory in the sense that it is defined by what it studies. Just to finish off, I'd like to reiterate that I feel the "matter and energy" definition pretty much describes what physics is. I believe this should be the goal of an encyclopedia entry, and not an all-inclusive idealized definition which may or may not be logically sound.

Now, I'm going to stop arguing for the case of a "rules-based" definition because, after more thought, it doesn't really address the real issue that I would like to argue for. Thus, for the sake of argument, let's say my new philosophical definition is: physics is the science that seeks to acquire knowledge of nature.

The problem lies in what this word "nature" means.

We can certainly say that it means, "matter and energy". That's good because then this definition can't be refuted based on its accuracy. It's also bad because this definition is only valid "now": it was not valid before matter/energy were discovered, and it will not be valid if those concepts are found to be wrong.
I would ALSO like to say that we can define "nature" to mean "everything". I think that this new definition, even with this meaning to the word "nature", negates most of O. Prytz's argumens above. This is because it only says that physics attempts to understand everything - not that it is possible. Given the opportunity, I believe physics will attempt to understand penguins just as well as it does the motion of particles. That is, given the opportunity, physics will try to absorb all the other sciences into itself.

Is this any better? Krea 16:08, 18 October 2006 (UTC)

Hi Krea, I think I am starting to see what you want to say. I still disagree with your definition, not because I don't like it, but because I think it is wrong: all of science seeks to acquire knowledge of nature; physics is just one of those sciences, covering a subdomain of the totality of natural phenomena. Also, I believe that we are trying to describe what physics is, not what physics may become some time in the future. I agree with you that given the opportunity, physics will try to absorb all the other sciences. But that is not what physics is now, and I strongly feel that we need to write about physics as it is today. HEL 18:21, 18 October 2006 (UTC)

It seems to me that we all now have a pretty clear idea of what the various points of view are, and that there's no point spending any more time re-stating and trying to entrench individual positions. Let's be more practical, and work on some actual text. Based on the discussions above, the remaining live viewpoints seem to be as follows:

1. The study-based definition/description

the type of scientific investigations that can be carried out, today, under the banner of the science of that name (based on the way in which the word is used in common English parlance, both by Physicsists themselves and by educated non-specialists).

For example: Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy.

2. The rules-based definition/description

The set of physical laws which many (probably most) physicists believe underpins the fundamental workings of the physical universe, knowledge of which is at present very incomplete but which may in the future become better understood, thereby allowing a broader range of phenomena to be mathematically described.

For example: Physics is the set of univeral laws which define, at the most fundamental level possible, the behaviour of the physical universe.

3. The historical definition/description

The older sense of Natural Philosophy.

Below is a further proposal for discussion which tries to cover both main angles. I would suggest we leave Definition 3 out of the lead paragraphs, and keep it for the historical section (which will immediately follow this one). I don't like this text quite as much as my original wording but if we don't compromise this discussion is clearly going nowhere. I've kept the 'practical' definition (definition 1) first, for comprehensibility, and I hope that's OK. I've also incorporated a variety of comments made above, but not all of them (not least since some suggestions are mutually incompatible).

Linas has requested that we find a citation for the statement that most theoretical physicists work on aspects of particle physics and related fields. That shouldn't be too hard. Actually, most are string theorists, although that's perhaps a bit too technical and specific for this article.

--MichaelMaggs 18:12, 18 October 2006 (UTC)

Focusing now on specifics - a revised proposal

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy. Physicists seek to understand the physical properties of the ~~universe~~ material world at the most fundamental level, normally by way of mathematical modelling of the behaviour of physical systems. Physics is therefore closely related to mathematics, which is the logical framework that allows for the precise formulation of these descriptions. The aim, however, is to go beyond describing physical phenomena, and to construct mathematical models or theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to support or refute the theory.

Some theories are of such significance that they are referred to as the laws of physics. Typically, these are physical principles that are believed to be common to all physical systems, or at least are of very general applicability. Some principles, such as Newton's laws of motion, are still generally called "laws" even though they are now known not to be of such universal applicability as was once thought. The word 'law' is a misnomer since even a law of physics could, in principle, be disproved by experiment. Other theories are more limited: they describe the behaviour of specific physical systems only, or are applicable only under certain circumstances.

Since one of the major goals of physics is the formulation of theories of universal applicability, on a broad perspective physics can be viewed as the set of univeral laws which define, at the most fundamental level possible, the behaviour of the physical universe.

Classical physics traditionally includes the fields of mechanics, optics, electricity, magnetism, acoustics and heat. The more recent fields of general and special relativity are also usually placed within this category. Modern Physics is a term normally used to cover fields which rely on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics and condensed matter physics. Although this distinction can be commonly found in older writings, it is of limited current significance as quantum effects are now understood to be of importance even in fields previously considered purely classical.

Physics research is divided into two main branches: experimental physics and theoretical physics. Experimental physics focuses mainly on empirical research, and on the development and testing of theories against practical experiment. Theoretical physics is more closely related to mathematics, and involves generating and working through the mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available. ~~Most theoretical physicists work on aspects of particle physics and related fields.~~

--MichaelMaggs 18:12, 18 October 2006 (UTC)

I could support this intro, except perhaps the final sentence. I'm sure that many theoretical physicists do work related to particle physics, but I'm not sure if most of them do. It depends, of course, on how you define theoretical physicists, but I know that there are quite a lot of people doing theoretical work (for example density functional theory) in condensed matter/solid state physics that regard themselves as theoreticians. I don't know how many they are compared to the particle physics gang, but I would guess that they're a significant fraction of the total. O. Prytz 18:48, 18 October 2006 (UTC)

Thanks, MichaelMaggs, for pulling it together! I am very happy with this intro except for two parts:

(1) In the first paragraph, ...seek to understand the physical properties of the universe...: this seems too biased towards particle physics / cosmology. I would prefer ...physical properties of the material world or something like that (maybe universe and its contents? I know "universe" technically includes the contents, but laypeople might interpret it differently).
(2) I think the last sentence is inappropriate, whether it's citably true or not. Do we need to get into theorist demographics in the intro?

HEL 19:10, 18 October 2006 (UTC)

OK, I have no problem with deleting the last sentence and changing 'universe' to 'material world'.--MichaelMaggs 19:38, 18 October 2006 (UTC). In fact, I've done it.--MichaelMaggs 19:48, 18 October 2006 (UTC)

Yay! :-) One grammatical pet peeve: "which" should be replaced with "that" in the first sentence. HEL 20:01, 18 October 2006 (UTC) Also in the second-to-last sentence of the first paragraph. HEL 20:03, 18 October 2006 (UTC) Also copyedit in paragraph 3: "the the" -> "the", "perpective" -> "perspective", and perhaps "theories of universal applicability" -> "theories with universal applicability"? HEL 20:06, 18 October 2006 (UTC)

Done the typos. The rest I think is grammatically correct (at least here in the UK). Let's see what others have to say.--MichaelMaggs 20:11, 18 October 2006 (UTC)

Sounds good. It can be improved, but all the content is there. My objections concern style and clarity, not content. I fully support this intro, though the following can be improved:

"...seek to understand the physical properties of the material world at the most fundamental level," is really just a shaky synonym for "concerned with the discovery and characterization of the universal laws which govern matter and energy". We're saying "Physics is concerned with X. Physicists seek X... usually using mathematical modeling." We're repeating X twice. If we like "physical properties of the material world" (I don't, it's verbose and indefinite) then use that in place of "matter and energy". "Universal" is a better word, I think, than "fundamental", but if we want to really throw "fundamental" in there, we should do so directly.
We say "physicists... use mathematical modelling", and in the next sentence we say "mathematical modelling can be used [to help do what physicists do]". Again, redundant.

This might be solved by replacing

...and energy. Physicists seek to understand the physical properties of the material world at the most fundamental level, normally by way of mathematical modelling of the behaviour of physical systems. Physics is therefore closely related to mathematics, which is the logical framework that allows for the precise formulation of these descriptions. The aim...

with

...and energy. Mathematics is important to the physicist; mathematical modelling allows one to precisely formulate descriptions of physical systems. The aim...

The question is perhaps whether the link to mathematics should be brought out so suddenly (no, I don't think that what we have now is a solution to this). Perhaps putting the theory/prediction first?:

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy. Physicists develop mathematical models and theories which predict how a physical system will behave. Mathematics is important in this process, as it allows them to formulate precise descriptions of the physical systems. The predictions made are then tested experimentally. If they are wrong, the theory is falsified; if they are right, the theory gains more support.

The next paragraph could start with something about the theories having much support, and it would flow into it quite well. This is my proposal for a revised lead paragraph. –M^T 22:43, 18 October 2006 (UTC)

I have to say I prefer the original for style. I understand your point about redundancy, but we're aiming here for readability, not the use of as few words as possible. Brevity runs the risk of reducing comprehensibility, especially to a reader who knows nothing about the subject and who won't be expecting to have to parse the text closely, word by word. Also, the wording you've proposed doesn't flow as easily.--MichaelMaggs 14:57, 24 October 2006 (UTC)

Omission reduces comprehensibility, but brevity increases it. I shortened, but I did not omit. You misunderstand brevity: it's not about reducing word-count, it's about giving the writing focus by eliminating the irrelevant. William Strunk:

Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. This requires not that the writer make all his sentences short, or that he avoid all detail and treat his subjects only in outline, but that every word tell.

Surrounding redundancy helps in the learning of individual words, yes, but this is not a concern here. The words we use are not obscure, and we define our terms explicitly. What makes you say that the terse is harder to parse? Strange, I found the old sentences cramped, non-cohesive. Where exactly is comprehensibility reduced? Where do words require careful parsing? Where is the flow interrupted? The latter, perhaps where we mention the importance of mathematics. I would have removed that sentence, since importance is made clear in "...develop mathematical models and theories...", but I didn't want to remove content. I copy the variants here. The original:

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy. Physicists seek to understand the physical properties of the material world at the most fundamental level, normally by way of mathematical modelling of the behaviour of physical systems. Physics is therefore closely related to mathematics, which is the logical framework that allows for the precise formulation of these descriptions. The aim, however, is to go beyond describing physical phenomena, and to construct mathematical models or theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to support or refute the theory.

The revised:

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy. Physicists develop mathematical models and theories which predict how a physical system will behave. Mathematics is important in this process, as it allows them to formulate precise descriptions of the physical systems. The predictions made are then tested experimentally. If they are wrong, the theory is falsified; if they are right, the theory gains more support.

What exactly is lost and gained and where? –M^T 06:54, 25 October 2006 (UTC)

Nothing is lost in content, but with short, staccato sentences something is lost in readability and flow. Perhaps the following would be acceptable. I've kept the word 'fundamental' in as well as 'univeral' as others seem wedded to it.

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy. Physicists formulate these laws as mathematical theories which attempt to model the behaviour of physical systems at some perceived fundamental level. The aim, however, is to go beyond describing physical phenomena, and to construct theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to verify or falsify the theory. --MichaelMaggs 15:35, 27 October 2006 (UTC)

Flow comes from good decisions about when to introduce certain concepts, about how to lay out your ideas. You don't get good flow by injecting "normally by way of" and "The aim, however, is to go beyond" and "Physics is therefore closely related to". You don't get it by making frequent allusions to and repetitions of what you've mentioned in the last sentence. You don't get it by frequent use of conjunctions and the like ("however", "therefore"). It's very easy for something that means very little to have great flow, or elegance, or whatever. Not that the above "means very little". The case there is poor layout. Have a look at the following:

Physicists make predections of how a physical system will behave. These predictions, in the form of mathematical models and theories, are then tested experimentally. If they are wrong, the theory is falsified; if they are right, the theory gains more support.

How does that sound? I think that it's a lot better than

Physicists formulate these laws as mathematical theories which attempt to model the behaviour of physical systems at some perceived fundamental level. The aim, however, is to go beyond describing physical phenomena, and to construct theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to verify or falsify the theory.

which communicates the same thing, but meanders through inconcreteness and... confusion. The first sentence is borderline nonsense: "Theories which attempt to model", "behaviour … at some perceived fundamental level". Not that I'm too fond of what I've produced by trimming this sort of thing. It doesn't explain how falsification occurs, why it's so important, and so on. It's just a superficial summary. And it isn't at all specific to physics. –M^T 20:09, 28 October 2006 (UTC)

I like this. I still have a problem with "matter and energy," but I think I'm getting used to it, since it doesn't bother me nearly as much now. A couple comments:

...on a broad perspective physics can be viewed as the set of univeral laws which define... - I think it should read ...on a broad perspective physics can be viewed as the [search] for the set of universal laws which define... (or some synonym thereof), since physics is a scientific search, not a court =O).

Under classical physics, I believe astronomy should be included. This is a bit of personal bias, and I may be getting my scientific history a bit wrong, but I think astronomers were/are generally classified in the same sense as most natural scientists.

My impression of modern physics was that it also included SR/GR. I don't know if there's a general consensus on this anywhere, but my undergrad treated them as such. Dunno if cosmology should also be included (again, personal bias), since it's partially a derivative of GR and partially its own field.

Though of lesser importance, I think this should address some of the cross/applied disciplines which are either popular or have long-standing relationships with physics (ie, biophysics, chemical physics (physical chemistry), geophysics, atmospherics (I don't know if this is the proper term), etc.) I think this is important, since the last paragraph sort of implies a distinct chasm between experimentalists and theoreticians, though applied physicists tend to be both. A quick shot at a treatment (goes after the last paragraph):

Applied physics is the term used to describe physics restricted to particular applications. These disciplines tend to be experimental in nature, but also perform extensive theoretical treatments of the subject. There are almost as many fields of applied physics as there are sciences, though some are more common in the public eye, such as insert other fields here.

Content-wise, this is okay and I think treats the subject fairly well. I think the biggest problem is its length, but there's not much that can be done about so varied a subject. Virogtheconq 01:04, 19 October 2006 (UTC)

I'd be happy with your suggestion of the [search] for the set of universal laws which define..., but Krea, for one, seems very keen to define Physics by the actual rules themselves. Let's see what he has to say on this. I wouldn't inlude astronomy within the text since it isn't traditionally included in classical physics. It could be mentioned as an application, though. There's not complete agreement about where relativity fits in, which I think is reflected in the propsed text. Not sure about an applied physics sentence being added here; this will be covered in more detail later in the article of course.--MichaelMaggs 14:57, 24 October 2006 (UTC)

Hmm, I'd always thought astronomy fell into "traditional" physics, given that many of the natural scientists/philosphers seemed to study it, but that could just be up to historical interpretation. The primary reason for including an applied physics section is (in my estimation) leaving it out may imply to the reader that experimental and theoretical is really all there is to physics, with no real crossover. At least, that's how it appears to me, but if it doesn't to you that's fine. Virogtheconq 02:16, 28 October 2006 (UTC)

Hi just a quick note, from the paragraph it seems that physical science proceed in this way: first theoretical work is done, then it is tested with experiments, this is not only misleading but wrong in many, famous, cases... expecially I would change these sentences "Experimental physics focuses mainly on empirical research, and on the development and testing of theories against practical experiment. Theoretical physics is more closely related to mathematics, and involves generating and working through the mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available." in something more orgnic.. I'm not a good writer, but I think something like "Experimental physics focus on empirical research, making experiments to test how energy and matter behave. Theoretical physics instead try to generate mathematical models to explain the results of the experiments or even ttry to find mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available." It's not well written but I hope you got my point.. Tatonzolo 21:57, 20 October 2006 (UTC)

There's nothing in there, so far as I can see, which sets out how physical sciences proceed, nor is there any attempt to do so. The text simply summarizes the respective roles of experimental and theoretical physicists (without any order being implied). Are you suggesting those statements are incorrect?--MichaelMaggs 14:57, 24 October 2006 (UTC)

No there is notthing wrong in the statement, probably I didn't like the statement "Experimental physics focuses mainly on empirical research, and on the development and testing of theories against practical experiment" since it seems to me that strips the possibilities for Empirical research to do new discoveries, not covered by models or even never thought possible (like the charm quark discovery, never theorized before, and no one was expecting to see that, there were no models to test).. but probably the statement is fine after all.. :-) Tatonzolo 18:41, 24 October 2006 (UTC)

OK, thanks. --MichaelMaggs 15:36, 27 October 2006 (UTC)

The Endgame

I have followed the discussions over the past month, and have spent a couple of hours this morning reviewing this page fully. We are now at a point of forming this situation up into a final order. This section was always going to be the most difficult to create, so in reality things haven't actually went too badly.

We now have a definition which I think it is worth putting out to formal review. I have left paras 2,3,4,5 out - I think it is worth pinning this first para down, and I would comment that the full text is perhaps a little too long, bearing in mind this will sit above the table of contents and virtually fills my screen ATM (for "big" articles the average seems to be around 200-350 words - this one is currently up at 400, and the MOS suggests it should be between 2 and 4 para's) - additionally we will have to make sure that the extended lead text properly dovetails with the intro text to avoid repetition or deviation.

So the lead section first paragraph text:

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy. Physicists formulate these laws as mathematical theories which attempt to model the behaviour of physical systems at some perceived fundamental level. The aim, however, is to go beyond describing physical phenomena, and to construct theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to verify or falsify the theory.

Editors Support, Oppose or Comments are welcomed on the text (and suggestions welcomed on a header picture to sit alongside this definition - probably not penguins!).

Support - it reads well, eloquently describing a subject that is notoriously difficult to "pin down". SFC9394 14:56, 28 October 2006 (UTC)

File:PrismAndLight.jpg

Diffraction of light by a prism.

Support --Ancheta Wis 16:09, 28 October 2006 (UTC).
Comment: Propose the free-fall image for the intro.
Comment: While this is acceptable, it can be improved. Some things bother me, like the imagery of theories attempting to model things as opposed to being models of things, inconcrete wording like "at some perceived fundamental level", and any statement that hints at definite truth (theories aren't verified, rather, support for them grows). It begins with what physics is, and deviates into what physicists do. My first comment here suggested that initial sentence, and then an expansion into the typical and the interesting subjects of physics, and how it differs from other sciences. I still prefer that to this. Relationship to the other sciences and what physics doesn't cover aren't mentioned. The public article states "...as well as the analysis of systems which are best understood in terms of these fundamental principles" (meaning not systems like penguins). This is inconcrete, but it sums up a very important point, one that we've argued over and might have failed to resolve, and do not mention in the lead at all. Perhaps some of this is hard to notice amidst what SFC9394 describes as eloquent language: "The aim, however, is to go beyond describing...". Satisfactory, but I'm still not content. Yes, we've spent 138k arguing over various aspects, discussing it all to death (right?), and shouldn't we put something out there to account for this work! No. We have a very diverse set of opinions, and an important precept that every voice, unless clearly insane, gets an equal say. There are no lead-editors here with proven experience and talent to decide things, and to quash discussions that aren't worth our time. If we don't have the patience or the heart to collectively rewrite/amend this intro 10, 20, or 50 times - well, we'll end up with a not-so-bad article that can be of some help to people, which might be ok with us. It's ok with me, I'm not expecting something great here. I would like it if we decided on what should be in the lead (do we need to list so many sub-fields? etc.) and what each paragraph should focus on - before we decide what to write, much less vote on it. I'd like: definition, elaboration of subjects covered (and not covered), difference between classical and modern; products: laws, discoveries, applications; process/method, where experimental/theoretical fits into it. –M^T 19:23, 28 October 2006 (UTC)
Comment: have the same concerns as M Tatonzolo 21:01, 28 October 2006 (UTC)

Oppose – (Noetica) I don't like the proposed definition at all. I'll analyse it sentence by sentence:

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy.

I am against this mention of matter and energy. It is simply not necessary to constrain the scope of physics in this way. In the history of physics, and in possible developments of contemporary physics, the categories matter and energy may not be so salient. I am also against saying that laws "govern them", as opposed to saying that laws govern their behaviour. (In fact, although I was earlier in favour of using this word govern, I now think that the word describe is preferable.) I also don't like characterization here; I think it is redundant.

Physicists formulate these laws as mathematical theories which attempt to model the behaviour of physical systems at some perceived fundamental level.

Again, while such mathematical formulation is deeply ingrained in contemporary physics, it is not essential to physics, construed as a study that arose almost three millennia ago, and continues to develop. There are circularities here: a relatively benign one in the mention of the activities physicists in the course of defining physics; and a more serious one in the mention of physical systems. Presumably what counts as a physical system is partly determined by what we take physics to be, so it is unreasonable to use the notion in defining physics.

The aim, however, is to go beyond describing physical phenomena, and to construct theories which can also predict how a physical system will behave.

Again, what are physical phenomena, exactly? Do they include the activities of penguins in caring for their eggs? Do they include mental events and processes? Do they include miracles (if miracles are taken to be possible, in any robust sense)? Physical phenomena are to be defined in terms of physics, so they can't be appealed to in defining physics. Also, the concern with prediction may not be essential to physics, in all of its variants.

These predictions can then be tested experimentally to verify or falsify the theory.

This concern with verification or falsification by experiment is not universal, either.

So I am not satisfied! As has been pointed out a few times already, we do not need to dwell on the hallmarks of science in general. That should be done at Science, or at Natural science. We can simply link to some more general treatment there. The question to be settled in our definition is, rather, what place and what role in the broad endeavour we call science is occupied by physics? In a general sense, it may be considered identical with all science that is concerned with the natural world; in a more day-to-day sense, it is identical with only a part of that domain. Why can't we capture that duality, which was, after all, close to the root of our interminable disagreements?

A note on the natural world: Few would dispute that physics is a science concerned with the natural world. The scope of this term natural is problematic; but I think we can use it, or use nature, quite safely. CS Lewis's Studies in Words (Cambridge UP, 2nd ed. 1990) includes a long analysis of nature (along with Latin natura, and Greek phusis, of particular interest for us), showing its many meanings and connotations. And many others have agonised over the meanings of the term. But we should have a good definition summarily set up for our treatment of physics, somewhere, that we can appeal to in a link, though I don't think the article Nature currently does the job. In any case, at least we can be quite certain that natural world does not exclude human-modified parts of the world, as someone thought it might earlier, I think.

Last, I should say that we can't do everything that seems connected with the task of furnishing a definition for physics. We have to cover what's essential, informative, and relevant beyond the characteristics of current physics. I think the proposal before us now fails to achieve this. – Noetica 00:22, 29 October 2006 (UTC)

I agree, this definition should be essential and to some extent "timeless". Some other points, like circularity of definition, aren't relevant since the definition really ends at the first sentence. We still have some conflict oven nature and matter and energy, so let's focus on them below. The distinction of laws 'governing X' vs 'governing X's behaviour' is unimportant. It's understood by default that when we say law Y governs X, we mean exactly that it governs X's behaviour. What else would it govern? –M^T 06:22, 29 October 2006 (UTC)

Matter and energy

The core definition,

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy.

has the following resilient point brought up against it:

"Matter and energy" unacceptably constrains the definition, instead, use "nature".

There are two groups of argument against this. The first is that "matter and energy" are acceptable. It is clear to the common reader and to the physicist what is meant: that fundamental stuff that all tangible/physical/non-mental complex systems are made of. HEL made a very good point, copied here, emphasis mine:

[...] In fact, as a particle physicist I would interpret matter and energy as a euphemism for fields and their interactions, which is about as fundamental as it gets -- the PR buzzwords of particle physics in the past five years have been "the study of matter, energy, space, and time" (see, e.g, the ILC consensus document from 2003 (pdf)). Going down to lower energies - condensed matter, fluids, etc - "matter and energy" still describes the building blocks. HEL

One supposed exception to "matter and energy" that was brought up was Lagrangians. I'm no physicist, but it seems that they have everything to do with the laws that govern matter and energy (physical systems), but correct me if I'm wrong. The second argument is that even if "matter and energy" is too constrained, the only proposed replacement, "nature", is worse. Here are arguments against "nature":

To many, "nature" has very strong connotation for biological things - documentaries of lions eating zebras, leafy jungles, and so on. Something to avoid.
"Nature" includes many types of systems, many types of things that have nothing to do with physics as we know it. Complex systems (like penguins) are currently not covered by physics, and there is no indication that they will ever be, in a practical sense, covered by it.

"Matter and energy" is the best we have. –M^T 06:22, 29 October 2006 (UTC)

Well, what about using the standard Wikipedia technique of listing the appropriate schools of thought. So far the following have been brought up in previous discussion:

Essentialism - here the approach is to list the essential components, say, matter and energy. But we see a dispute here.
James Clerk Maxwell's 1874 popularization Matter and motion: "physical science ... relates to the order of nature, or the succession of events". Unfortunately "nature" has apparently been overloaded with several millennia of connotations. But need that apply?
Feynman's approach of Simplicity and Symmetry in his characterization of physical law. Note: in the etymology of nature Homer himself used the word nature as characterization.
- "...and yet there are other things of interest in the world. Even the artists appreciate sunsets, and the ocean waves, and the march of the stars across the heavens. There is then some reason to talk of other things sometimes. As we look on these things we get an aesthetic pleasure from them directly on observation. There is also a rhythm and a pattern between the phenomena of nature which is not apparent to the eye, but only to the eye of analysis; and it is these rhythms and patterns which we call Physical Laws." --R.P. Feynman (1965), The Character of Physical Law, page 13, MIT Press ISBN 0-262-56003-8
Macrocosm and microcosm - the idea, dating from antiquity, that the laws of physics apply across multiple scales, from the very large to the very small. This happens to be the program for both cosmology and particle physics.
This ostensive list has no end. As Noetica points out, this isn't going to get settled in one paragraph.
Has anyone considered formulating an extensional definition instead?

--Ancheta Wis 08:11, 29 October 2006 (UTC)

I'd like to stress that "matter and energy" aren't quite meant to be an essential definition. Though (I think) they cover everything that physics is, the point here is that the reader will understand what we (all of us) are getting at. HEL calls them "a euphemism for fields and their interactions". I, an easily-recognizable stand-in for "that fundamental stuff that all tangible/physical/non-mental complex systems are made of". There's not an ounce of confusion to be had here, the reader will know exactly what we mean. It's both an ostensive and complete definition. (This covers points 1, 5, and 6). Points 2 and 3 are directed towards the scientist, and not towards the average reader. 3 isn't definite about "nature", it talks of a "rhythm and pattern". I don't think that any specific source will help resolve this issue, as many people define physics in different ways. The definitions vary by intent, desire to stress a point, audience, writer bias, and so on. We need to argue over the merits of the proposals for our audience. "Macrocosm and microcosm" doesn't seem a good replacement for "matter and energy", if that's what's meant by point 4. In short, I think that "matter and energy" is the answer to points 1, 5, and 6, and that points 2 and 3 do little to address the concerns that I brought up regarding our readers' perception of "nature" as opposed to "matter and energy". –M^T 16:39, 29 October 2006 (UTC)

In this posting I'll comment only on the last contribution by M. [The first in this section (I added one above)–M^T]

M isolates the following suggestion for analysis: "Matter and energy" unacceptably constrains the definition, instead, use "nature". This is something like what I endorse: I started an earlier attempt at a definition like this: Broadly, physics is the science of nature: the science concerned with describing the basic constituents of the natural world, and specifying the laws governing their behaviour, singly and in combination. I am now unsure about "governing", but I don't regard that as a central issue. I still think my attempt was not too bad, and I'll defend it in light of what M has said. M argues that matter and energy are indeed acceptable, in the eyes of both physicists and the general public. But how can they be acceptable, if we want our definition to fit historically, and across cultures, and for all future developments? An early Newtonian working the same way might have characterised physics in terms of corpuscles and their interactions in real time and real Euclidean 3D-space. And that definition would, as we can now see clearly, fail on account of its restriction to the best available theory in Newton's time. What is wrong with appealing instead to the basic constituents of the natural world? Surely physics has always wanted to address these, whatever they turn out to be as a matter of empirical discovery or theoretical postulation. M later raises two useful points against using "nature" in our definition. According to the first, the term evokes visions of wildlife documentaries and the like – so it is too narrow for our definition. But it seems to me that any such connotation is quickly dismissed when we mention specifically "the basic constituents of the natural world." No one is going to take this the wrong way, surely. M's second point is that "nature" is too inclusive – so it is too broad for our definition (most facts about penguins, for example, being outside the proper scope of physics). But I answer that this is to prejudge in favour of what I have called narrowphysics, which by its very definition excludes biological, chemical, geological, and other "high-order" facts. I have gone to some trouble to argue for this being just one of two equally acceptable understandings of the term physics; and after all, my candidate definition continues like this, precisely to accommodate narrowphysics, ecumenically: In most current uses of the term, physics is understood as more limited: there are special sciences (chemistry, biology, psychology, etc.) which are treated as if they were autonomous and not as parts of physics. And my definition therefore allows for both "readings" of physics: the primary, philosophically robust one, and the secondary but far more practical and everyday one, used by working physicists and those who talk about their work. I then conclude with a caution about the distinction: This exclusion of some complex features of nature is a matter of mere historical fact and mere practical convenience; it does not limit the original scope of physics as the universal science of nature. So I simply disagree with M's conclusion that "Matter and energy" is the best we have. We can indeed appeal to nature, the basic constituents of the natural world, or some similar formulation, and so avoid being hostage to blinkered and historically uninformed notions of what physics must amount to. It is not essentially to do with matter and energy, any more than it is essentially empirical. But it is, and always was, and always will be, the study of the basic constituents of natural world: the description of them, and the laws underlying their behaviour. – Noetica 10:09, 29 October 2006 (UTC)

Cassiopeia A - a spherically symmetric remnant of the 1680 supernova

How about a paraphrase of Feynman's "phenomena of nature"? Say, 'Physics is the study of the phenomena of nature'. That would include time and events, and nature includes space, matter, and by implication, energy. That would also cover macrocosm and microcosm --14:32, 29 October 2006 (UTC) [That was posted by Ancheta Wis]

What is a "basic constituent of the natural world"? What is "phenomena of nature"? The first point here is that this could be many things that aren't physics: concepts, universal biological behaviours. Perhaps "basic physical constituents"? No, that won't do. The second point is this: as far as we know, what are the basic constituents of the natural world? Matter and energy. Maybe this will become more specific in the future, maybe it will be refuted. We shouldn't take a step upwards to ambiguity for fear of this. It's not that physics must be this, it's that physics is, to the best of our current understanding, this. I also want to stress again that physics is not a superclass for biology, psychology, and so on. "As if they were were autonomous" indeed! They are autonomous. They were never part of the physics of today. As we know it now, physics studies the fundamental and avoids complex systems. Science studies nature, physics studies only the basic constituents. I reject "broadphysics". Broadphysics is science. –M^T 16:39, 29 October 2006 (UTC)

We seem to be going around in circles again. As an simple, easily understandable (in a hand-wavy way), the definition,

"Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy,"

is perfectly acceptable to me. Many people, however, adhere to a more general definition - and it is this one that I would also like to see included. None of these definitions are wrong. Saying that physics does not include biology, or such statements, is meaningless because that is merely how you have DEFINED the words physics, biology, science etc. It is a fact that some people believe, and many have believed, that the essential analysis of physics is all of nature: penguins and all. This is, of course, a belief: they believe physics to be able, one day, to study penguins. As editors of this article, when discussing definitions of physics, we should responsibly state all mainstream definitions of the word physics. Merely because some people don't believe this definition to be true, or some people define "science" to be this and "physics" to be something more specific does not warrant its exclusion.

Physics may never be able to describe penguins, true. However, this is not the issue. We are not here to argue beliefs. The fact is that this belief exists, and a significant number of respectable physicists would not be against such a definition. That is why it should be included.

There seems to be no issue here, to me. Let me conclude: The definition is not explicitly wrong. It may be wrong, but enough people believe it to be true to warrant its inclusion. Now, unless somebody can either demonstrate that this definition is explicitly incorrect, or that it is not, in fact, a widely held belief, it should also be included. Krea 19:53, 29 October 2006 (UTC)

"is merely how you have DEFINED the words physics" - we're not arguing over a meta-topic of how we've defined physics. We're arguing over what physics is and what it covers. You argue for the inclusion of all popular definitions. Here's how we would include them: "some physicists define physics as the study of all of nature. Others disagree, and argue that…", or perhaps "some believe that by understanding the smallest constituents, we can then extrapolate this understanding onto systems that are, practically, infinitely more complex". I can't even comprehend how physics could tell us anything meaningful about a penguin, as biology etc. can. I would very much like for you to enlighten me in this. I don't think that you appreciate the difference between understanding the behaviour of X, and understanding the behaviour of what X is composed of. If you think that the lead should state that physics covers everything directly, then please give an example of physics work that covers complex systems. I'm not talking about simple chemical reactions, and I'm not talking about parts of supposedly complex systems. I'm talking about whole living organisms, and using the laws of physics to explain evolution. When scientists talk about physics covering all of nature, I think that they're getting at the fact that all of nature is composed of the stuff that physics studies, and the general universality of physical laws. –M^T 02:54, 30 October 2006 (UTC)

"I can't even comprehend how physics could tell us anything meaningful about a penguin, as biology etc. can. I would very much like for you to enlighten me in this. I don't think that you appreciate the difference between understanding the behaviour of X, and understanding the behaviour of what X is composed of."

I may not be able to enlighten you I'm afraid, merely because I am neither knowledgful nor clever enough to; but whether I can or cannot is besides the point, as I shall soon argue. You are correct, I draw no distinction between understanding X and understanding the constituents of X (X_i): if I have the COMPLETE laws for the interactions of X_i, I believe that I can deduce the behaviour of X. Let's not argue about this point specifically: you believe one thing, I believe another. The fact is that we just don't know which is correct. My point is that some people have taken the belief that I also share as being reasonable. Therefore, such a definition should also be included. Noetica argues against your other criticisms of the definition below, but this is the main one: you cannot agree to the "superior" position of physics as the father of all the other sciences. Fair enough, but whether you or I cannot comprehend the assertions of a particular definition is not important. The fact that respectable people have already argued that such a definition is reasonable should be sufficient for its inclusion. That is it. I don't have to convince you that it is reasonable: that has been done through the academic community (thats not to say that it is universally endorsed, however). Krea 13:26, 30 October 2006 (UTC)

Let's not argue about this point specifically: you believe one thing, I believe another. Whether or not physics is capable of describing the behaviour of complex systems is a rather crucial point that we shouldn't... uhm, ignore because we disagree. Yes, you can hypothetically deduce the behaviour. The problem is, the deduction would take an incomprehensibly long time and be mind-numbingly complex. Simulation of protien folding is being carried out at 190 teraFLOPS over 178000 computers. A protien, by comparison to an ant, much less a human, is an absolutely trivial system. A system that is closed. A system that doesn't need interpretation. You'd need what amounts to a post-singularity AI to pull off using physics what your average biologist does. Quote me a few respectable physicists that explicitly state that we'll be able to understand some complex system if we understand physics. –M^T 01:59, 31 October 2006 (UTC)

What was meant was for us to not argue about beliefs: unless you can provide sound physical arguments on why your belief is in fact true, what is the point in either of us trying to "convert" the other? You seem to equate hard/impractical with impossible. I, however, do no such thing: there is a world of difference between saying something is hard, and saying something is impossible. Whilst I agree that practically we may never deduce a penguins behaviour, as long as it is hypothetically possible to do this (so that, in principle, we could predict their behaviour), then I regard those penguins as falling under the domain of physics. Again, that is not true if you regard physics as "what we can predict now or reasonably expect to predict in the future", but this is only one particular view of what physics is: we could equally say physics is "what we can predict now or what is possible to predict in the future". Examples? All physicists who reject dualism: Newton would be the most famous, I guess. Krea 11:06, 31 October 2006 (UTC)

Once more I'll narrow my focus to M's contribution. M, you conclude your last post this way: "Science studies nature, physics studies only the basic constituents. I reject "broadphysics". Broadphysics is science." OK. You are stating a partisan position that is characteristic of working physicists, and of those who discuss the work of working physicists. I want to allow for your position in our definition. Our definition would certainly be incomplete if it did not respect that position. But it would also be incomplete if it ignored the more philosophically durable and more timeless position. Yes, broadphysics is science. And the consequence of that? Well, many do believe that an idealised, perfected physics encompasses all of science (that is, science understood as the study of natural world). In sum, I am offering an ecumenical and conciliatory solution. You are putting forward a partisan proposal. But – with all respect – such a proposal perpetuates the very problem we are wrestling with. It is not a solution at all. As for specifics, I call on you to address my point about medicine and dentistry, which gives a close analogy to the situation with physics and the special sciences. I also call on you to address what I wrote a little above:

"An early Newtonian working the same way might have characterised physics in terms of corpuscles and their interactions in real time and real Euclidean 3D-space. And that definition would, as we can now see clearly, fail on account of its restriction to the best available theory in Newton's time. What is wrong with appealing instead to the basic constituents of the natural world?"

If you will not do this, I don't know why I bother making the effort to develop particular arguments which remain forever unanswered. Reassertions of partisan views will advance us not at all. Excuse the sharp edge, here: we really do need to start answering each other. – Noetica 22:13, 29 October 2006 (UTC)

There are two arguments here. First, that physics is basically science or that it can do what the other sciences do, which is handle very complex systems. This I reject. Second, that "basic constituents" is a good substitute for "matter and energy". I agree that "basic constituents" is correct, but it doesn't explain what a "basic constituent" is.

Your dentistry argument is circular: "[Physics concerns the entire natural world, so the other sciences are part of physics.] Dentistry is a health science, and likewise, biology studies a part of the natural world. Therefore, biology is a subset of physics." This is wrong. Dentistry, podiatry, and optometry are all subsets of medicine. Physics, biology, and psychology are all subsets of science: the study of the natural world.

Review your use of "partisan". Also note that the middle ground between two positions ("let's include both definitions") isn't at all conciliatory. I'm not discussing working physicists, and I'm not quite sure what the term means. Does it mean physicists who actually do work in physics? You admit that broadphysics is science. You believe that physics will be able to explain the entire natural (non-imaginary) world. I think that this is absurd. Will physics explain evolution for us? The structure of the mind? The mating behaviour of penguins? Physics is driving towards the simple, and not the complex. If you understand how particles behave, you won't suddenly understand all systems composed of those particles.

My response to your newtonian point is a question: what are the "basic constituent of the natural world"? Atoms? Those 10000 distinct rules that certain parts of nature seem to abide by? Strings? Love? Waves? Equations? Ideas? Be specific! "Basic constituents" is meaningless to someone who doesn't quite understand what physicists think the world is made of. There are people out there who think that everything is composed of energy - and I don't mean energy, I mean "souls" or "willpower" or whatever other image is conjured in the mind of someone who doesn't understand what energy is. I don't want an ambiguous definition to serve as fodder for stupid ideas of what physics might be. Physics is concerned with describing what physicists currently believe are the basic constituents of the natural world. Let me ask you this as a hypothetical question that I'd like to keep seperate from my current arguments: if, somehow, a much better approach to describing the basic constituents came about that had no use for any of the findings of physics, but did not invalidate physics, which science would we call physics? –M^T 02:54, 30 October 2006 (UTC)

Noetica's reply to M

Reply to M (– Noetica)

It seems to me that the discussion between M and me is exactly the sort of dialogue we need right now. It is difficult and time-consuming, but at least we can address central issues in a focused way, and we cannot come to a lasting solution without doing that. I therefore continue the discussion, working through all of M's last reply to me. In what follows, I quote M in italics, and respond in normal type, further indented.

There are two arguments here. First, that physics is basically science or that it can do what the other sciences do, which is handle very complex systems. This I reject.

That is not exactly my position. Let me state it clearly. The term physics has two main meanings:

A broad meaning (more philosophically respectable and relatively timeless), according to which it is the science of the natural world, and is therefore identical with science itself (that is, with science construed as the study of the natural world), and including the so-called special sciences.
A narrow meaning (more useful for day-to-day practical purposes), according to which it is what remains of natural science, after we remove the special sciences: those sciences well-adapted to specific classes of complex systems in the natural world (like chemistry and biology).

Now, the advocate of the first meaning will argue that chemistry, for example, just is physics "handling very complex systems": that chemistry is a branch of physics, reducible in principle to very basic physical principles, but usually proceeding with its own pseudo-autonomous laws and postulated entities. This M rejects; and this I do not reject.

Second, that "basic constituents" is a good substitute for "matter and energy". I agree that "basic constituents" is correct, but it doesn't explain what a "basic constituent" is.

I am glad M agrees that "basic constituents" is correct. But I don't see that a definition using this term needs to explain what the basic constituents in fact are. That would be to prescribe specific theoretical content for physics, and a definition doesn't need to do that. If an early Newtonian had done that, or a Cartesian, or an Empedoclean, the resulting definition would be hostage to a theory that was doomed to failure. For all we know, matter and energy may not truly be basic constituents or basic categories. Adherence to that paradigm may turn out to be the very thing that impedes progress in physics. Not so with basic constituents, as a cover-all formulation.

Your dentistry argument is circular: "[Physics concerns the entire natural world, so the other sciences are part of physics.] Dentistry is a health science, and likewise, biology studies a part of the natural world. Therefore, biology is a subset of physics." This is wrong. Dentistry, podiatry, and optometry are all subsets of medicine. Physics, biology, and psychology are all subsets of science: the study of the natural world.

My dentistry argument, which gives what I still consider a useful analogy, is not circular. And I don't see how M makes a case for that claim. Here is how I presented it:

Consider medicine. It is, roughly, the applied science concerned with the health and disease of the body, yes? So, given that the teeth are a part of the body, medicine should be concerned with the health and disease of teeth, right? Well, yes and no. Conceptually and broadly, dentistry is a part of medicine, and the teeth are one of medicine's concerns. It is valuable to think that way about the scope of medicine, at first. But then, as a practical and historical fact, dentistry and teeth are considered separately.

First, podiatry and optometry are not "subsets of medicine". If you have a broken foot, or a sliver of metal in your eye, you don't go to a podiatrist or an optometrist. You go to a medical practitioner. But if you have a broken tooth, you go to a dentist. That's why I confined my analogy to dentistry.

Second, I agree: physics, biology, and psychology are all subsets (so to speak) of science: the study of the natural world. And if you hold that by its broad definition physics is identical with science (as the study of the natural world), then biology and psychology are all subsets of physics. (And physics – broadly construed – is still technically a subset of physics, but not a proper subset; physics narrowly construed is, of course, a proper subset of physics broadly construed.)

Third, I offer another analogy, to work synergistically with the dentistry–medicine analogy. We could define fruit broadly and biologically as the mature ovary of a flowering plant. This would include cardamom pods, apples, mangosteens, zucchini, tomatoes, and pumpkins. We could alternatively define fruit narrowly as the mature ovary of a flowering plant, generally sweet and fleshy, prepared and eaten in certain particular ways or in certain particular dishes. This would include apples, mangosteens, and perhaps tomatoes. Fruit narrowly defined are a proper subset of fruit broadly defined. The broad definition is durable, timeless, philosophically and scientifically respectable – and against everyday usage. The narrow definition is changeable, subject to the forces of culture and fashion, philosophically and scientifically dubious – and perfectly in accord with everyday usage. Both definitions of fruit are indispensable; and they coexist happily.

Review your use of "partisan". Also note that the middle ground between two positions ("let's include both definitions") isn't at all conciliatory.

I have reviewed my use of the term partisan. I still intend to use it. Imagining myself to be a partisan, I would certainly favour the broad definition of physics exclusively, if a choice were forced. But there is no forced choice, and I will not restrict myself to my favoured interpretation of the term. I want to see both interpretations represented in our combined definition. M links to middle ground, which is quite an interesting move, I think. But I offer in return a link to the fallacy fallacy. The mere fact that there exists some fallacious argument with P as its conclusion does not prove that P is false. There is, in any case, some uncertainty about whether what I offer is "middle ground", in any relevant sense. I simply say, and sincerely believe, that the term physics is quite properly used in both a broad and a narrow sense. I prefer the broad sense, for an encyclopaedic definition: but I readily allow that we have room for both senses, and that it would be wise to include both. Isn't that conciliatory?

I'm not discussing working physicists, and I'm not quite sure what the term means.

O, let me explain. If I ask you what work you do, and you reply "I'm a physicist", then you are a working physicist.

Does it mean physicists who actually do work in physics?

It means those who identify themselves as physicists, for the purposes of practical everyday communication.

You admit that broadphysics is science.

Yes.

You believe that physics will be able to explain the entire natural (non-imaginary) world.

No. I'm not committed to such a belief. That is the hope of some who call themselves physicists: those who aim at a theory of everything. But I can say something about such a theory: it would have to be, not just a completed narrowphysics, which reconciled quantum theory and general relativity, and all the rest, but also an account of how broadphysics was unified by reductions of its treatments of complex systems (in chemistry, biology, etc.) to narrowphysics. If it did not achieve this, it would not be a theory of everything.

I think that this is absurd. Will physics explain evolution for us? The structure of the mind? The mating behaviour of penguins?

I don't know. There have indeed been people who call themselves physicists and who claim that such reductions from biology and other special sciences are possible, in principle. I suppose they are, in principle. For philosophical purposes, this possibility of reduction is enough to bring chemistry, biology, etc., into the fold. But let me ask this in return: will quantum physics ever be able to explain, or predict the timing of, the emergence of a supernova, or a tsunami? Unlikely! We rely on quite different, macro-scale principles to do such an explanation or prediction. Nevertheless, we allow that astrophysics, and the physics of seismic activity, and quantum physics are all part of an overarching physics, yes? I'm just doing the same, except more consistently.

Physics is driving towards the simple, and not the complex.

More accurately, all science (that is, physics broadly construed) seeks to reduce complexity to simplicity.

If you understand how particles behave, you won't suddenly understand all systems composed of those particles.

Agreed. Not suddenly; and possibly not ever, in some domains of enquiry.

My response to your newtonian point is a question: what are the "basic constituent of the natural world"? Atoms? Those 10000 distinct rules that certain parts of nature seem to abide by? Strings? Love? Waves? Equations? Ideas? Be specific!

But that is hardly a response at all. As I have said above, our definition would be better if it did not specify such particular content for physics. We might turn out to be wrong! It doesn't matter, for a good robust definition, what the basic constituents truly are. By the way, in the physics of Empedocles the two opposing forces love and strife are basic constituents, along with the elements fire, air, earth, and water (see http://plato.stanford.edu/entries/empedocles/). I would count Empedocles' theory as genuine physics. It doesn't have to be true physics, or good physics, to be physics.

"Basic constituents" is meaningless to someone who doesn't quite understand what physicists think the world is made of.

I disagree. I think the notion of basic is easily understood, as is the notion of constituent; and so is the combination of these two notions.

There are people out there who think that everything is composed of energy - and I don't mean energy, I mean "souls" or "willpower" or whatever other image is conjured in the mind of someone who doesn't understand what energy is. I don't want an ambiguous definition to serve as fodder for stupid ideas of what physics might be.

Yes, they are a worry, aren't they? But I don't think that those neo-Empedocleans will be taking our article on physics very seriously, or reading it attentively. It is more important that we say clearly what is true than that we try to second guess what crazy interpretations might be attached to what we say.

Physics is concerned with describing what physicists currently believe are the basic constituents of the natural world.

(Well, that is surely circular!) Physics aims to explain the natural world. Sometimes it succeeds, sometimes it fails. If we include some particular content in our very definition, citing what physicists currently happen to believe about the natural world, we are needlessly hostage to an opinion that may turn out to be mistaken. Furthermore, we exclude earlier beliefs that are surely part of the endeavour of physics, even if they are now found to be mistaken. Like Empedoclean physics, or Newtonian or Cartesian physics.

Let me ask you this as a hypothetical question that I'd like to keep seperate from my current arguments: if, somehow, a much better approach to describing the basic constituents came about that had no use for any of the findings of physics, but did not invalidate physics, which science would we call physics?

If we define physics broadly, as I propose, then current physics would be able to yield gracefully to the new, superior physics. And it seems perfectly correct that it should do so, yes? But if physics is defined in terms of matter and energy, then it is unclear what should be done. Our definition will be shown to be inadequate: or at least, it will necessitate our finding a new term for the new superior science. It's like this: if Empedocles had defined physics as the study of earth, air, fire, water, love, and strife, and a new science came along that made no use of these notions, but they still retained what little explanatory and predictive ability they had, Empedocles could not call the new science physics. Silly Empedocles!

– Noetica 10:57, 30 October 2006 (UTC)

It's nice to see someone else has a problem with the "matter/energy" definition. I've recently thought that some chemistry fields are probably just as concerned with "matter/energy" as some physics subsets, perhaps moreso, which is probably another reason why it needs to be redefined. Suggestion: It seems as if much of the debate over broadphysics is somewhat centered in the historical versus modern interpretation of "physics." Here's a concept for the introduction that glosses over a definition by first admitting that the field is not well-defined, and addresses it in a somewhat historical context. I admit it is an attempt at a middle ground that incorporates multiple definitions, but hopefully in a way that provides some reasoning for including (all of) them; also, as a concept, it naturally suffers from many literary/linguistic issues. The ellipsis defines a place where I think the original attempt can be integrated with this version.

Physics is one of the natural sciences. Historically, physics attempted to characterize the behavior of the natural world (see natural philosophy); however, as the general state of science advanced and specialized fields emerged, it became more narrowly focused on the study of matter/energy/Lagrangians. The advent of modern physics and its applicability to other fields has broadened the definition to a more general study of penguins with orthopedic issues...

—Preceding unsigned comment added by Virogtheconq (talk • contribs)

M's reply to Noetica

Reply to Noetica (–M^T)

There are three positions here. First, that physics is the the superclass of all the other sciences. This position is satisfied by the following definition:

Physics is the study of the natural world.

The second is that physics studies the base constituents:

Physics is the study of the basic constituents of the natural world.

The third is that physics studies matter and energy, or that "base constituents" is unclear to someone who doesn't already know what they are:

Physics is the study of matter and energy.

It seems that we agree on position 2 over 1, but some arguments made lead me to think otherwise. Though I would enjoy further discussion, I appeal to precident in Wikipedia to resolve the dispute between these.

The Wikipedia categorization system does not place biology or even chemistry under Category:Physics. Physics, chemistry, and the earth sciences are described as equals under Physical sciences, Category:Physical sciences, and Fields of science. An argument to change this categorization shound be posted in the relevant place - probably wikiproject science - where a more diverse group can participate. Until it is resolved there, we should avoid this argument here and wait or proceed according to what is established, namely that what is being referred to as "broadphysics" is science in general, and that physics deals specifically with the basic components of complex "physical" systems (namely matter and energy), and complex systems that are best understood in terms of physical law (for example, the orbits of large masses of matter).

Though the argument should now be moot, I'd still like to respond to some points:

First, podiatry and optometry are not "subsets of medicine". If you have a broken foot, or a sliver of metal in your eye, you don't go to a podiatrist or an optometrist. This is incorrect. If you have a broken foot, you'd go someone who knows enough to fix it. Same for a sliver in the eye. And who do you go to when you have some complex problem of the foot? A podiatrist. A complex problem of the eye? An optometrist. And a complex problem of the teeth? A dentist.
You incorrectly apply the fallacy fallacy. I did not assert that your position "both should be included" was wrong because of the fallacy, just that the argument "we disagree, so the correct course of action is to include both" was fallacious. The middle ground fallacy, like the opinion fallacy ("our positions, since they seem to be irreconcilable, must be opinions, therefore it is useless to argue") tends to end discussion prematurely, and I wanted to avoid that.

The conflict we should focus on is between the second and third positions. I'll try to get to the heart of the matter. It seems to me that you're defining a word, while I'm describing its referent. The word physics may mean "the study of basic material constituents". What this article talks about, however, is a very certain (and diverse!) study of matter, energy, fields, the role of time and space, and so on. If against all odds all of this is overturned, and the word physics is used to describe some new field, then the contents of this article will be moved to [old physics], and we'll discover that a definition like "...base constituents" is actually incorrect in light of what the rest of the article is about. Word versus subject. If we want to mention that the study of fire, earth, wind and water (or whatever) was called physics, we'd note that under history, and we'd describe how the word physics referred to different things at different times. Today, physics refers to a study of matter and energy (or fields and their interactions), and it's that study of matter and energy that this article talks about. I agree that the word physics refers to "...base constituents", but my disagreement stems from the fact that this article is about matter and energy (which incidentally are the base constituents) and is not about the base constituents - whatever those may be.

–M^T 01:59, 31 October 2006 (UTC)

Noetica's reply to M

Further reply to M (– Noetica)

In my last reply to M I reproduced and analysed all of the text to which I was responding. I note that M has not done this with my text, and has often failed to engage with points that I have made – in some cases for the second time, even though I asked for a response. If I have not done justice to any of M's points, I'll do so on request. But I expect the same from M, and I suggest that this is a reasonable expectation. Here are my responses to some of what M has written inreply to me.

M identifies three positions, or what we I will prefer to call tenets. I'll change some wording (like base to basic) for uniformity:

1. That physics is the superclass of all the other sciences.

2. That physics studies the basic constituents.

Exactly what the third tenet amounts to is unclear. It seems to be a disjunction of two elements. I'll separate the two elements this way:

3a. That physics studies matter and energy.

3b. That "base constituents" is unclear to someone who doesn't already know what they are.

I gather that M agrees with 2, 3a, and 3b. And M denies 1.

I agree with 1, if physics is taken in one of its two senses (the broad sense).

I agree with 2, provided that we amplify it this way (from my earlier definition): ...concerned with describing the basic constituents of the natural world, and specifying the laws governing their behaviour, singly and in combination.

I agree with 3a, but only as a matter of current fact, but not as defining physics.

I disagree with 3b.

M writes: It seems that we agree on position 2 over 1. If this means that the editors contributing here agree on 2 but deny 1, I don't think it is right. There are those who agree with me that the term physics has more than one meaning, and according to the broader meaning it includes the other sciences. This is supported by another encyclopaedia that I have cited, and by a very eminent philosopher whom I have cited, and by historical fact, and by etymological considerations, and by a consideration of claims that the laws of other sciences may be reduced to those of physics construed more narrowly, or that the facts dealt with by other sciences are supervenient on the facts of physics construed more narrowly. So it is wrong to assume a consensus where there is none (yet!).

Choosing not to address specific challenges I raise against M's position, M decides instead to appeal to Wikipedia precedent: the category system has it that physics is just one science among many, and so rules in favour of narrowphysics alone. So anything contrary to that ruling in our definition is improper, and ought to be taken up elsewhere, "probably wikiproject science".

I completely reject such a move, and once more call on M to take up the challenges that I have issued. It is as if any book on the philosophy of physics that identified physics broadly should be excluded from a library using the Dewey system, because it broke the rules of classification. The Wikipedia categories are a similar system for preliminary classification. Quite properly! Very practical, for encyclopaedic "bookkeeping": but not apt for dictating how a thoughtful and nuanced analytical article must proceed, or what definitions it may or may not develop.

In any case, my proposed definition does allow for physics to be defined in the way of the Wikipedia categories (and to pursue the consequences of that definition in almost all of the article) – as well as another way. The situation is to be compared with the article Fruit, in which two senses of the key term coexist perfectly happily, reflecting the reality of its use in different contexts.

M seems to think that the appeal to Wikipedia precedent is decisive ("the argument should now be moot"). I think it is extremely weak.

M nevertheless responds to some of my points:

First, podiatry and optometry are not "subsets of medicine". If you have a broken foot, or a sliver of metal in your eye, you don't go to a podiatrist or an optometrist. This is incorrect. If you have a broken foot, you'd go someone who knows enough to fix it. Same for a sliver in the eye. And who do you go to when you have some complex problem of the foot? A podiatrist. A complex problem of the eye? An optometrist. And a complex problem of the teeth? A dentist.

The exact dealings that podiatrists and optometrists have with the parts of the body they are concerned with differ in different parts of the world. Is it really the case that a podiatrist would set a broken bone – of the ankle, say? Or that an optometrist would remove a splinter of metal penetrating into the body of the eyeball? Not where I come from; but nothing much depends on the matter. I am happy to concede just about anything concerning podiatrists and optometrists. I do note that M has not addressed the point I wanted to make with my dentistry analogy. I will make it again more clearly, if asked to do so.

M goes on:

You incorrectly apply the fallacy fallacy. I did not assert that your position "both should be included" was wrong because of the fallacy, just that the argument "we disagree, so the correct course of action is to include both" was fallacious. The middle ground fallacy, like the opinion fallacy ("our positions, since they seem to be irreconcilable, must be opinions, therefore it is useless to argue") tends to end discussion prematurely, and I wanted to avoid that.

Well, from this I really can't tell why M raised the matter of the middle ground fallacy in the first place. To the extent that M does level such a charge against me, with inaccurate description of the process by which I arrive at my conclusion, I respond with an accusation that M falls into the fallacy fallacy. But this is all very mixed up, and is probably best set aside as unproductive.

M continues:

The conflict we should focus on is between the second and third positions.

Now, I take it this means that we should choose between characterising physics as dealing with basic constituents, and physics as dealing with matter and energy. My own position is quite clear: physics – past, present, and future – always attempts to deal with basic constituents. It happens, at present, to identify these basic constituents as matter and energy. But it didn't always, and it may not in the future. For this reason, a definition in terms of matter and energy is manifestly weak.

M's view is more complex:

I'll try to get to the heart of the matter. It seems to me that you're defining a word, while I'm describing its referent.

On the face of it, at least, these two activities seem pretty much the same. To define the word dog is pretty much the same thing as describing its typical referent – the thing we typically pick out by using the word dog, yes? But M is making a subtle point:

The word physics may mean "the study of basic material constituents". What this article talks about, however, is a very certain (and diverse!) study of matter, energy, fields, the role of time and space, and so on. If against all odds all of this is overturned, and the word physics is used to describe some new field, then the contents of this article will be moved to [old physics], and we'll discover that a definition like "...base constituents" is actually incorrect in light of what the rest of the article is about. Word versus subject.

Now, this is fine as far as it takes us. But it doesn't take us very far! The article is not exclusively about current physics: it is about the study that is always, in all ages, to be called physics. If it were exclusively about current physics, and our term physics were to be restricted to mean only that, we could not meaningfully speak of the history of physics. We would have to speak of its precursors, and give them new names. For example, we could not speak of the physics of Empedocles, or the physics of Newton, Descartes, or Laplace. Why on earth would we want to make life so hard for ourselves? Taken to its extreme, this way of proceeding would identify the term physics with physical theory exactly as it is constituted in 2006, and we would need to find a new term in its place next year! Or, of course:

If we want to mention that the study of fire, earth, wind and water (or whatever) was called physics, we'd note that under history, and we'd describe how the word physics referred to different things at different times.

I just think this is an absurdly inefficient way to go. There is a continuity in a certain science, from earliest times to the present day, and beyond. That science is always concerned with the basic constituents of the natural world, whatever we understand them to be as this science progresses. Why on earth should we not give this unified endeavour the single name physics? What advantage can there possibly be in restricting things so that we lose all generality, consistency, and continuity?

No case has been made for such a strange move, other than the spurious suggestion that our readers may be confused by the phrase basic constituents. Why should this be so? Even M admits that one of the alternative words – energy – is subject to dangerous misunderstanding and abuse. I don't share that concern; but I wonder why M wants to use energy in a definition, if it is thought to be so hazardous.

M writes:

Today, physics refers to a study of matter and energy (or fields and their interactions), and it's that study of matter and energy that this article talks about. I agree that the word physics refers to "...base constituents", but my disagreement stems from the fact that this article is about matter and energy (which incidentally are the base constituents) and is not about the base constituents - whatever those may be.

But no: physics identifies different basic constituents at different times; but it always deals with what it takes to be basic constituents. I am perfectly happy for the article to go on with a detailed discussion of matter and energy, as it addresses the different theories and concerns of current physics. But in our definition, and in our brief historical survey, such a restriction is unwarranted, dogmatic, inefficient, and (yes!) partisan. – Noetica 12:48, 31 October 2006 (UTC)

M's reply to Noetica

I have not replied to each of Noetica's paints specifically, nor do I plan to. If I reply to each sentence with a paragraph, we'll see that this discussion soon becomes unmanagable. Sight of the central point will be lost as we argue over whether a podiatrist mends broken bones or not. Central arguments will be spread out over the reply, and instead of replying to logical groups of them in unison, we'll end up replying to small chunks that might not be as sensible on their own. I don't want that.

I've identified two groups of argument (tenet 1 and 2) that Noetica seems to be making, and I've replied to them both as groups. Here are the tenets again:

1. Physics is the superclass of all the other sciences.

2. Physics studies the basic constituents.

3a. Physics studies matter and energy.

3b. "Base constituents" is unclear to someone who doesn't already know what they are.

I've replied to 1 by appealing to precident, and the suggestion that such a discussion doesn't belong here. Noetica suggests that the categorization system is (mere) bookkeeping. In anticipation, I linked Physical sciences and Fields of science, articles that are clearly not bookkeeping. They are non-volatile articles that demonstrate that there is some form of consensus among editors that physics is not a superclass, but that science is. If Noetica disagrees, then our argument should end here. There's no sense in arguing between tenets 2 and 3 if we can't get this resolved. I don't think that this draft page is the proper place to argue a subject that affects all of the other science articles and the categorization system. We can't have [physics] implicitly claim that it's the superclass of biology and psychology, while other articles like [physical sciences] claim them to be equal. Either Noetica should abandon tenet 1 in regards to this article, or we should take the discussion to Wikipedia talk:WikiProject Science. There, I'll be happy to reply to whatever points are made, assuming that someone else doesn't respond first.

So, in short, which definition do you propose?

Physics is the study of the natural world.
Physics is the study of the basic constituents of the natural world.

If it's #2, then we'll continue the conflict between tenets 2 and 3 here, and no longer spend time on arguments that are essentially for tenet 1. If it's #1, then we'll continue that discussion at Wikipedia talk:WikiProject Science. Is this reasonable? –M^T 21:00, 31 October 2006 (UTC)

Noetica's reply to M

I agree with M that the discussion would become unmanageable if we responded to each sentence with a paragraph. But I have raised a few matters that are simply not addressed in M's responses. I'll not repeat them, since that seems futile.

M recapitulates the tenets that we both worked to identify:

1. Physics is the superclass of all the other sciences.

2. Physics studies the basic constituents.

3a. Physics studies matter and energy.

3b. "Base constituents" is unclear to someone who doesn't already know what they are.

And M says, concerning 1:

I've replied to 1 by appealing to precident, and the suggestion that such a discussion doesn't belong here.

Well, where precisely does such discussion find a home, if not at this page set up for just this purpose? Here is an excerpt from an anonymous contribution in the last topic at Category_talk:Physics, which was, interestingly enough, Definition of Physics. I add my highlighting in bold:

I utterly disagree with the given definition of physics.

Energy does not interact with matter but particles, people, animals interact with each other. It is a bit like saying pears interact with apples.

When energy interacts with a bicycle, does this mean that the bicycle is beginning to move? No. When a person interacts with a bicycle (pushs the pedals) the bicycle begins to move. Energy is an abstract concept that does not interact with anything!

I would switch to the etymological definition :

Physics is the science of nature

but I would add

In practice, Physics is the science performed within the scientific method as applied by the physics community and defined by the works of physicists like Gallilei, Descartes, Planck, Einstein, Dirac or Feynman. [Note: This is equivalent to "working physicists". – N]

because I believe a science is not only defined by its object but also by its methods and the community of people doing it.

This thoughtful and comprehensive contribution continues at some length. It received the following dismissive reply:

I think you're trying to change the wrong page, because this intro is to a category and shouldn't really be too elaborate. I think no one has changed it since like a year, becuase it jsut isn't important, so I reduced it to a minimum. A complete definition and anything else about physics should be found simply in the article about physics. Cheers. Karol 12:07, July 14, 2005 (UTC)

(!)

That was the end of the discussion: a diversion to our article, Physics.

Look, I've spent a lot of time on this. (So has M; so have many others.) When my detailed analytical arguments are met with a suggestion that I take them elsewhere, I feel that I am right to object. Elsewhere is not the place: this is the relevant place (a page set up for precisely this purpose), and Physics is the relevant article. No, M: the category articles and the science articles are not all "mere" bookkeeping. And they quite rightly locate physics among the sciences, as in a sense one of the specialisations. I have no quibble with their doing that. Nor do I have any quibble with our doing that. But I want to close off future dissent and bickering by allowing that, in an important sense, physics occupies a central and general role. In a way, all other sciences are a part of it. Why can't that be allowed? Just as in the article Fruit. Why should it be that the editors of that article can sort such things out, but we cannot?

M writes:

Either Noetica should abandon tenet 1 in regards to this article, or we should take the discussion to Wikipedia talk:WikiProject Science. There, I'll be happy to reply to whatever points are made, assuming that someone else doesn't respond first.

Excuse my scepticism, and see the points I make above, illustrated with the example of discussion at Category_talk:Physics. Don't pass the buck; deal with the issue here.

M asks:

So, in short, which definition do you propose?

1. Physics is the study of the natural world.

2. Physics is the study of the basic constituents of the natural world.

If it's #2, then we'll continue the conflict between tenets 2 and 3 here, and no longer spend time on arguments that are essentially for tenet 1. If it's #1, then we'll continue that discussion at Wikipedia talk:WikiProject Science. Is this reasonable?

No, it is not reasonable, as I argue above. What definition do I propose? I've given it twice already. Here it is again, the same in its essentials, but modified by further consideration, partly reflecting the discussion since I proposed it:

Broadly, physics may best be thought of as the science of nature: the science concerned with identifying the basic constituents of the natural world, and the laws according to which they combine and interact to form complex systems. However, in most current everyday usage, physics is taken to be more limited, since there are special sciences (chemistry, biology, psychology, etc.) that deal with various kinds of complex systems using their own methods and theories. Physics is, for everyday practical purposes, the rest of science after these special sciences are taken out; and physics is the science that focuses more on the basic constituents and less on the complex systems that they form.

– Noetica 00:32, 1 November 2006 (UTC)

But I have raised a few matters that are simply not addressed in M's responses. I'll not repeat them, since that seems futile.

I'm perfectly willing to respond once we decide where we want to continue which discussion. I'm not up to discussing two tangled points at once. I'm not saying "take your arguments elsewhere". That's a dismissal. I want us to choose the correct forum, and I don't think that this backwater talk page is suited for a discussion about whether the other sciences are subordinate to physics.

I know that this discussion is important and might give rise to emotions, but I ask you to proceed in a reasonable manner. Calling me partisan because I have an argument that contradicts yours, accusing me of "passing the buck" because I'd like to argue with you on another page, and so on - this form of argument is not productive, and is unwelcome.

A discussion of the categorization of physics belongs in a place where we can get a diverse set of people contributing to the argument. Do you think that subcategorizing biology and psychology under physics has no effect on them? That people who have been categorizing these pages aren't interested in contributing to such a discussion? The notion that biology is a subset of physics is not trivial.

You link me to a discussion. An anonymous editor was unsatisfied with the definition and thought that the category page was the right place to bring up discussion. As far as changing the definition of physics, Karol was correct, the right place to do it is the talk page of physics. But as far as changing the definition in a way that affects many other very major pages, well, that sort of discussion just doesn't belong here.

Regardless, you seem to be against having this discussion there. Fine. What I want is more than two people contributing. I'll try to solicit more contributors. Meanwhile, onwards with discussing physics as the superclass of biology etc. I think that this deserves a new section, so see below. –M^T 11:53, 1 November 2006 (UTC)

M, by participating in the discussion here you might reasonably be taken to believe that it is the proper forum for such discussion. It is unreasonable and provocative that, when confronted with clear and sustained argument against a position you favour, you then seek to divert the discussion to another page altogether. Let's be clear about what we're doing: this is THE page that a group of serious editors interested in physics have agreed will be the place for threshing out the issues that were causing trouble for the Physics article. We have set out, first, to find a consensus definition for physics. If that is not your intention, you might like to withdraw from discussion here. (I hope you will not decide to withdraw, though.) As for how our deliberations might affect other pages, that's not our prime concern at all. If anything, we have a claim to being the experts who are doing the hard yards, and our precedent should carry weight elsewhere. All that said, I for one am not proposing anything that will have consequences for other pages. Read my proposed definition, and note that I incorporate the everyday, practical definition neatly as a part of it; and I justify that everyday definition. That narrow component of my definition is perfectly in accord with the bookkeeping classificatory régime used elsewhere (and in accord with the rest of the Physics article to follow, I should add). But we are doing more than bookkeeping: we are, I hope, aiming at a well-founded, durable, and philosophically sound definition for a major part of the human intellectual endeavour. I await your responses to the points I have made, and to my proposed definition. I have proceeded in a reasonable manner, and I call on you to do the same. – Noetica 12:52, 1 November 2006 (UTC)

If it is not clear where I belive this discussion should take place, then I am at fault. I think that this is not as good a place as wikiproject science. And I agree, I did and still would like to divert this discussion there. If more people - chemists, biologists, and so on - join in this page's discussion of how those sciences relate to physics, then I may be wrong: this may well be the forum I'd like it to be. I agree that the discussion is important, and that our precident should carry weight. Would you agree that for it to carry more weight, we should have more people? If so, perhaps you might support my message at wikiproject science? There was my diversion of this discussion, and my delay in answering your points. Have I been otherwise unreasonable? If so, please let me know where. You can leave a message on my talk page if you'd like. –M^T 13:23, 1 November 2006 (UTC)

The language of nature as she is spoke

- (see: English as she is spoke :-)

In parallel to the effort of definition ongoing, above, I quote from G. Toraldo di Francia (1981) The Investigation of the Physical World ISBN 052129925X , an English translation of the 1976 L' Indagine del Mondo Fisico. di Francia quotes Galileo's Assayer

"Philosophy is written in that great book which ever lies before our eyes, I mean the universe, but we cannot understand it if we do not first learn the language and grasp the symbols in which it is written. This book is written in the mathematical language, and the symbols are triangles, circles, and other geometrical figures, without whose help it is humanly impossible to comprehend a single word of it, and without which one wanders in vain through a dark labyrinth."

di Francia then notes

"Literally, therefore, it is nature that forces its own language on the observer, and not the other way around."

To paraphrase, mathematics is the language of nature and Galileo is directing us to learn the language of nature, however she speaks. Thus physics might be thought of as that science which seeks to learn the grammar of nature. Other sciences can also concern themselves with the nouns, verbs, adjectives, adverbs of the language of nature. The grammar of nature can also be called the characterization of nature. --Ancheta Wis 08:27, 1 November 2006 (UTC)

Physics as a super-science

Physics is the superclass of all the other sciences.
Physics studies the basic constituents.

It seems that I agree with tenet 2 (as far as "physics" the word is concerned), and disagree with position tenet 1, while Noetica believes that both should be represented in this article. I argue that tenet 1 is incorrect and that this article should not be based on it.

To say that physics is the superclass of the other sciences confuses the study, and the subject of study. Complex systems like penguins are made up of matter and energy, so penguins and the laws that govern them are subordinate to matter and energy, and the laws that govern them. Biology studies penguins; physics studies matter and energy. It is a mistake to assume that because the subjects of these two sciences have a certain relationship, that the sciences themselves share this relationship.

The historical argument for tenet 1 runs as follows: Physics was called natural philosophy. As time went on, other sciences split from physics. Though they split, they are still technically 'under' physics, because physics is the study of the natural world.

I call into question every part of this argument. Natural philosophy became natural science, not physics - though a large portion of what it studied was later studied by physics. This point undermines the supposed historical support for defining physics as the study of nature. The wider group, "natural science", is the study of nature. Furthermore, "nature" as defined by natural science refers to relatively simple systems, and not complex ones such as humans and networks of humans - hence the split between the natural and social sciences. The other sciences did not "split" from physics - physics is one of the components (just like chemistry and the earth sciences) of 'natural science', which spawned out of natural philosophy, which in turn spawned out of philosophy. So it seems that philosophy is the source! But I won't argue for this - my point here is that there seems to be no historical support for calling physics 'all study of the natural world', or saying that other sciences developed from it, or that they are subordinate to it. Physics is the study of very simple systems (matter and energy), and biology, chemistry, psychology study certain complex systems. Biology or chemistry did not emerge out of some discovery in physics. And, going back to my first point, two studies need not relate to each other as their subjects relate to each other. –M^T 13:00, 1 November 2006 (UTC)

Can I state for the record that, not aiming this at you M, or anybody in particular, that all arguments against this definition based on another definition are idiotic. You may not argue that this definition is "wrong" because science studies nature, and physics is only a subclass of science, for example. This is merely one person's definitions contradicting another's, which is clearly fatuous. Now, I really don't understand the objections to this "broad" definition of physics. There are only two ways to legitametely attack the broad definition: to either

show that is explicitly incorrect because it contradicts known facts, or
in the absence of such arguments, argue that it is not a widely accepted view.

Firstly, yes, the historical argument is a little shaky, but these such arguments are always very poor. Now, M, you say that:

Complex systems like penguins are made up of matter and energy, so penguins and the laws that govern them are subordinate to matter and energy, and the laws that govern them. Biology studies penguins; physics studies matter and energy. It is a mistake to assume that because the subjects of these two sciences have a certain relationship, that the sciences themselves share this relationship.

From the wording of this sentence, your view is incorrect; but I think I know the argument that you are trying to make, which is actually valid. Let me first explain why this is incorrect. By the definition of the word "knowledge", if I know everything about a system's constituents and their interactions, it therefore follows that I know everything about the system itself (whether we can practically acquire this knowledge is of no concern - all that concerns us is whether it is possible to do this in principle). Proof is by induction. Using the fact that I know how 2 constituents behave, I therefore know how a further constituent interacts with these two. Continuing in such a manner, I know everything about the complete system.

The problem comes when we apply this to things that are conscious, for it seems that such an argument must break down somewhere. Perhaps what you mean to say, M, is that penguins are further composed of something else that will never be explained by physical law? Anyway, many people have tried to resolve this, such as Descartes, but to no avail. I merely contest that it is not known whether the laws of physics do, or do not, apply to "complex systems", such as penguins, in a manner in which their behaviour may be deduced and predicted (both because of the limits of our intelligence in applying known laws and discovering new ones). However, I do believe that it is a significantly held belief amongst past and present academics that the entirety of nature will be described by physics alone (Ancheta Wis, amongst others, has just given us an argument that seems to support this view).

The broad definition, I then challenge, survives both conditions. Let me also say that if it is included, it must be made explicitly clear, for fear of misinterpretation, that it is merely a widely held belief, not a fact.

Finally, some people have argued that this article should only discuss what physics is now, and leave such arguments of future possibilities alone. This is an acceptable argument, but not one that I like: I see no reason for such a view (as long as we don't satisfy either of the two conditions of exclusion above) in an article that aims to be as comprehensive as possible. Krea 13:49, 1 November 2006 (UTC)

Krea argues against what I think are some very basic assumptions on my part. I think that the points made are easily overturned:

It is perfectly acceptable to use established definitions in arguments about definitions. Krea confuses this with unestablished definitions, as if I were using my own definition to support my definition. Not the case. The definitions for science, natural sciences, and so on are established - and these definitions, to me, seem very sensbile. I see no reason for me to avoid using them as I have used them above.
Krea poorly analyzes my argument (quoted italics above), and concludes that it is incorrect. It is not. My argument quite obviously attacks a path to a conclusion, not the conclusion itself. I think that I am very correct in saying that you can't use the relationships between the subjects to prove a relationship between the studies. Other means of arriving at the conclusion are still available, in fact Krea offers one:
Induction - though deduction might be what Krea meant. Krea suggests that if I know the behaviour of A and B, which compose C, that I will know the behaviour of C. The mistake is in assuming that I will automatically know the behaviour. For very simple things, this knowledge comes easily. However, for complex things, something else is required: skill in interpretation. Krea by analogy suggests that if I know all the words in a novel, that I will understand that novel, that if I memorize the specification for a programming language, that I will know any program, and so on. No, a keen sense of interpretation is needed here. Krea's premise that we know a complex system if we know its parts is incorrect.
No, I believe that consciousness obeys physical law - but there's that keen sense of interpretation again! I wouldn't base my argument on such indefinite ground as our inability to explain consciousness. My point is that it will be an extreme stretch of the interpretive powers of humans to use physical laws to understand protiens, and then exponentially more difficult to understand cells, and then exponentially more difficult to understand ants, and so on: humans, the human mind, social networks of human minds. That human physicists could do this is absurd. That physicists would attempt this seems equally absurd. I would like a few reputable sources quoted specifically on this issue. I want to hear the words "one of the goals of physics is to understand penguins", where "penguins" may be any complex system: ants, hurricanes, trees, humans, human minds, societies, languages.
Krea suggests that by quoting another participant here, that this proves a widely held view. Proper sources, please.
Hypothetical uses of physics should give way in the lead section to actual, current uses of physics. Does Krea dispute this?

I believe that I've shown that Krea's argument survives eithor of the two described 'attacks'. If something is unclear, I'm prepared to elaborate. –M^T 22:37, 1 November 2006 (UTC)

Typo in Intro?

Hi. Was reading, found this sentence second paragraph of the Introduction category: "For example, chemistry is the science of matter (such as atoms and ) and the chemical substances that they form in the bulk." To me, it looks like there is either an extra 'and', or there is a noun missing inside the parenthesis. Anyone know what the editor was going for there? Or where this comment should go, if not here? ^^;; CrispyDruid 15:51, 1 November 2006 (UTC)

"...atoms and molecules)..." perhaps? The comment should perhaps have gone on the physics talk page instead of here, but no harm done. It's not too important since that whole section will be reworked soon anyway. Krea 16:16, 1 November 2006 (UTC)

A few comments - request editors to read (and respond to)

We have had over 13,000 words written in the 4 days since I attempted the mind focusing request for votes/comments. I will give my honest opinion here - the entire discussion reads as a very large tail chasing exercise. Discussions and contributions from editors are not going to be forthcoming when there are, in total, over 36,000 words on the subject of a 350 word introductory few paragraphs. I am almost tempted to say that this section should be shelved for the moment unless things start moving forward. As I alluded to in my Endgame comments above, this is a piece of detail that is notoriously difficult to pin down - to the extent that there is no right answer. Unless we can all agree on that, produce draft introductory words, allow the process of refinement and iteration to take place on those words until we arrive at something that is broadly acceptable to most, then I don't see any future in these discussions. They are tantamount to semantical, metaphysical, philosophical debate - and words like those are notorious for being areas that allow people to write 100k+ words on how to define what exactly opposite means – and then have someone else come along and write another 100k on why they disagree.

The process isn't helped by the mediawiki software and it's very poor abilities when it comes to allowing a long and complex discourse to be followed easily.

Self evidently this is a complex thing to define - but if we honestly can't come up with something in an efficient manner then I would lean towards putting it on the back burner and getting some of the more straight forward areas of the article improved - if the current process continues indefinitely then all you folks who are putting in a lot of valuable time and effort creating these 36,000 words will have effectively been wasting your time - I don't want that to be the case - thus we need to make use of what we have in the bag to start focusing down onto specifics - if we don't then I fear it is all going to have been in vain. SFC9394 22:59, 1 November 2006 (UTC)

Yep. This will take a long time if we have only 3~ people contributing. I think that it's a no-brainer that physics is the study of matter and energy, and that this article is about a study of matter and energy and not a just any old fundamental constituents. I find the arguments against this weak: "but the historical definition of natural phylisophy is the study of nature, therefore physics is the study of nature" - physics isn't natural philosophy, and we aren't talking about historical definitions, nor hypothetical definitions. We're talking about an introduction to what the rest of this article talks about. Want to define how a word should be used? That's wiktionary. This article isn't about unknown and perhaps even unknowable fundamental constituents. It's about a science - a body of method and knowledge about a certain thing - which we use to understand how atoms, and gravity, and light, and matter in general - and other universal things behave. Unfortunately, because of wikipedia's nature (and because of a lack of participation, and the cycle involved there), we have to use a confusing thing called logic to explain our positions, and because it's so confusing, it takes a long time and many repugnant words. Want a summary that avoids nuance and tact? Here's mine:

Uh, physics isn't the study of nature. We call the study of nature "science", or "natural sciences". The ridiculous elitist position that physics will be able to explain, say, penguin mating habits or society or language is... well, ridiculous and elitist. And unfounded. I want sources to back up this claim, and I want them to specifically agree with it. I could be wrong! Maybe the world does see physics as the answer to all our problems! You never know.
Whatever was called "physics" before, or whatever we'll call "physics" in the future - this article is about a study of matter and energy, and how we came to where we are in it. Wannna talk about how the word physics should be used? Wiktionary. Or start an article about the word. Or an article about unknown hypothetical constituents. This article talks about a certain study of matter and energy, and right now, we happen to call that study "physics".

How's that? Productive? Who knows. I've never been in an argument where I didn't gain insight and practice, so I enjoy argument no matter the length, but I too can see that we've been arguing about this for a while. I think progress has been made, but that might not be important if noone follows along. So let's attempt this new style, and see where it takes us. Hostile argument seems to attract readers. Perhaps we can call a vote for consensus, after both sides are sufficiently polarized against each other, to see which one wins. –M^T 00:08, 2 November 2006 (UTC)

This whole discussion hinges on this "penguin argument". So, why don't we try things the other way around? Now, M, you attacked some of my points quite personally and foolishly in my opinion, but I will let them pass for now.

"Uh, physics isn't the study of nature."

Why?

"We call the study of nature 'science', or 'natural sciences'."

Silly argument. This is just an arbitrary definition that is no more justified than calling physics the science of nature.

"The ridiculous elitist position that physics will be able to explain, say, penguin mating habits or society or language is... well, ridiculous and elitist. And unfounded."

Wrong. Try to listen to the arguments being made. I have said that it is believed by a significant amount of respectable academics that physics will ultimately describe all objects. Your claim of the contrary is as equally unfounded. Can you come up with an argument based on known facts on why physics will never be able to, in principle, describe penguins? No, I didn't think so. Therefore why should anybody accept your position that physics is definitely not about penguins when that is merely a belief?

"This article talks about a certain study of matter and energy"

Wrong. This article is about physics, not matter and energy. You have your priorities wrong. Physics is the fundamental subject that is currently about matter and energy. To suggest that this article is about the study of matter and energy, which we currently call physics is insulting to me as a physicist, and I bet to almost every physicist here. I am a physicist. So are many people here. Ultimately, this is our article. You have said you are not a physicist. Whilst your views are welcome, who are you to dictate what our article on our subject is about? I am sticking my neck out here in second guessing the attitudes of the other physicists here, but I feel strongly about this particular point; so if the rest of you physicists disagree with what I have said, then I want nothing more to do with this article.

If your main argument against the broad definition is that physics will never study penguins, then you are on very shaky ground. That is mere belief, just as the contrary is also belief. Justify this assumption and I will have no grounds for a counter conjecture. Krea 01:43, 2 November 2006 (UTC)

Physics isn't the study of nature because it's the study of matter and energy [fields and their interactions, etc.] Physics != science. Science = the study of nature. Therefore, physics != the study of nature. Though it is one of several studies of nature. Other wikipedia articles contradict your position, and you havn't cited at all. However, I can say that it's the study of matter and energy. That's self-evident by the contents of this article. Want to dispute that? Ok. Some citations: mw, 'click physics', a bunch of dictionaries at reference.com.

You constantly confuse disputed definitions and established definitions (and opinion and logical argument). Look at the other wikipedia articles, dictionaries, etc. "Physical sciences" and "science" are defined as the study of natural phenomenon. How do you define science? "Science is physics and vice-versa"?

I don't have to prove that physics will never describe all of nature. The burden of proof (see also negative proof) is on you to back up your claim that it can or will, or that anything that may be called physics is about penguins and other complex systems.

Welcome to wiki. The article is not yours. Anyone can join in, even non-physicists. Can you imagine what the cold fusion article would look like if we left it to cold fusion researchers? Being a physicist is good for providing information, but not for making judgements about certain things that may affect your pride. That you're "insulted" by my argument that physics is the study of matter and energy is interesting (you must have been aghast when you opened up those dictionary links), but irrelevant. I'm not dictating anything. I'm arguing, just like you. Your "if others don't agree with me, then I want nothing more to do with this article" is humorous. I too will have nothing to do with this article. In fact, I'll leave wikipedia! The internet! I'll abandon social communication in general! Come on now.

You should spend more time backing up your position that physics is the study of base constituents. The biggest argument for "study of all of nature" and against "base constituents" seemed to be "but that's your opinion/made up definition". You have the reasons and citations that back up my position, perhaps you can offer something of the sort for yours?

Don't worry so much about my personal and foolish attacks. SFC9394 brought up an important point: that the argument should move faster. And be easier to get involved with. Hence this experiment in quick, tactless argument. Don't take it personally, I'm only 'attacking' your beliefs, arguments, and manner of argument, not you. –M^T

Response to SFC9394

What about opening up the edits to the Physics/wip page, instead of reverting on sight? Why would it be bad to allow parallel edits of the entire page, instead of waiting for consensus on one word or one sentence at a time? Why not just lay down the TOC as agreed-upon, and then open up the Physics/wip page for contributions, as in the rest of Wikipedia?--Ancheta Wis 00:41, 2 November 2006 (UTC)

Alternatively, we could just ask Physics/wip contributors to just edit the main article, and let the talk:Physics/wip page serve both the current Wikipedia page and the putative wip page. I propose adding a note welcoming contribution to the current main article. --Ancheta Wis 08:46, 2 November 2006 (UTC)

For example, this might be added to the banner on the Talk:physics page:

You are welcome to use the points on the Talk:Physics/wip page to improve the Physics article.

SFC9394, here below is an opportunity to call for a vote of approval, etc. --Ancheta Wis 11:41, 2 November 2006 (UTC)

Yet another plea for pluralism and consensus (– Noetica)

OK, yet again I am going to respond, implicitly at least, to what M has said – and even more to what M has not said. This is not because I think others' contributions are unworthy of analysis. In fact, Krea is calling for the same sort of broad, pluralist approach as I am, and responding to other editors as we should be. And I must say I am impressed with contributions from Ancheta Wis, which are so resourceful and creative in their reaching for a way to a consensus solution. But M is, it seems, the main champion of a narrow and (I fear I must add) unresponsive line on the crucial matter of definition.

I have presented a definition three times, modified the last time by the discussion we have been having. I have specifically called on M to respond to it in the form I give it, to no avail. The definition I propose includes, and even supports, the narrowly focused one that M favours, and I have made every effort towards conciliation and consensus, with a definition that has these properties. How can it be reasonable that such a definition is completely ignored?

Now, M censures Krea for not providing citations. But when I provide them, they too are utterly ignored! To add to the injury, M will be happy with discussion here, until it crosses boundaries that M has set up, whereupon we are told that the discussion should be moved to another page! Well, I'm for keeping the discussion here. And for the record, I'll now assemble in one place citations that support the broad aspect of the conciliatory definition that I propose:

Citation 1

From Encarta, the Physics article, Scope of physics section:

Physics is closely related to the other natural sciences and, in a sense, encompasses them. Chemistry, for example, deals with the interaction of atoms to form molecules; much of modern geology is largely a study of the physics of the Earth and is known as geophysics; and astronomy deals with the physics of the stars and outer space. Even living systems are made up of fundamental particles and, as studied in biophysics and biochemistry, they follow the same types of laws as the simpler particles traditionally studied by a physicist.

Citation 2

From a hard copy of Encyclopedia Britannica (from the 1980s), the Philosophy of Nature article, Philosophy of Physics section:

Inasmuch as the binding forces of chemistry can now, at least in principle, be reduced to the well-known laws of physics, or calculated from quantum mechanics,[...], chemistry can henceforth be considered as a part of physics in theory if not in practice.

Citation 3

From the same Encyclopedia Britannica (but a different author), the Physics article, lead material:

Perhaps the ultimate aim of physics is to comprehend the properties of the fundamental constituents in a single master plan and from it to deduce the properties of aggregates of particles and all macroscopic phenomena. Certainly the search for such a grand scheme lies at the forefront of contemporary physics.

[Compare Wikipedia's article on physics searching for a theory of everything.]

Citation 4

From the very eminent and influential American philosopher W.V.O. Quine, Theories and things, 1981, p. 99:

If the physicist suspected there was any event that did not consist in a redistribution of the elementary states allowed for by his physical theory, he would seek a way of supplementing his theory. Full coverage in this sense is the very business of physics, and only of physics.

Citation 5

From another philosopher, endorsing and amplifying Quine's view, Jaegwon Kim, one of the world's most respected theoreticians of the relations between physics and the special sciences, The layered model: metaphysical considerations, circa 2001, online at www.institutnicod.org/Reduction/The_Layered_Model.rtf , p. 19 :

Physics, as Quine aptly put it, is the only science that, by its very nature, aspires to "full coverage" – a comprehensive description and explanation of all phenomena of this world. Nothing is outside its concern and attention, and it's not for nothing that we think of it as the most fundamental and general of all the sciences. The domain of physics includes all that there is, and the special sciences are so-called because their domains are specially restricted subdomains of the universal domain of physics. As we saw, this fact is appropriately reflected in the Oppenheim-Putnam hierarchy, by their requirement that each level includes all higher levels, which implies that the bottom level, of which physics is in charge, includes all higher levels. [...] So let us begin with the universal domain, U, of physics. It is populated by bits of matter, their aggregates, aggregates of aggregates, and so on [...]

Now, I once more present my proposal for a definition that respects the views presented in these citations:

Proposed consensus definition:

Broadly, physics may best be thought of as the science of nature: the science concerned with identifying the basic constituents of the natural world, and the laws according to which they combine and interact to form complex systems. However, in most current everyday usage, physics is taken to be more limited, since there are special sciences (chemistry, biology, psychology, etc.) that deal with various kinds of complex systems using their own methods and theories. Physics is, for everyday practical purposes, the rest of science after these special sciences are taken out; and physics is the science that focuses more on the basic constituents and less on the complex systems that they form.

And again I make observations for editors here to consider:

This definition is comprehensive, and timeless.
It is understandable, and not misleading.
It includes, and what's more explains and justifies, a more restricted definition that some have favoured.
Consequently, further evidence anyone might present in favour of that more restricted definition simply supports this one as well.
This definition neatly hands over to the remainder of the article, which quite properly will be mainly concerned with physics narrowly construed.
Avoiding talk of matter and energy in this definition enables us to speak meaningfully of earlier physics which did not use those concepts; and future, and merely possible, physics that may not use them either. We want talk of mediaeval physics, or 30th-century physics, or Klingon physics, at least to mean something.

I don't say that my proposal is perfect. In fact, I'd probably want to change details myself, now. But I do suggest that it is worth taking seriously.

I've had just about enough of this, and I'm sure I'm not alone. If the case that I assemble here receives only scant response, or responses that ignore its carefully marshalled detail, or irrelevant digressions, or directions to discuss our core business at another forum, I'll end my involvement here. With regrets. Life, as I have had occasion to point out elsewhere in Wikipedia, is too short. – Noetica 10:47, 2 November 2006 (UTC)

First, some minor points in response to the third paragraph: I'm not sure which directly relevant citations you've provided before, but if I'd ignored them, then I am at fault. You're indignant in every one of your responses regarding my request to take an argument to a greater audience, even though I withdrew the request when I saw that it upset you:

Regardless, you seem to be against having this discussion there. Fine. What I want is more than two people contributing. I'll try to solicit more contributors. Meanwhile, onwards with discussing physics as the superclass of biology etc. I think that this deserves a new section, so see below

Which point did you choose to respond to? Did you wait for my new section? No, you wanted to continue the argument over locale. (And you still hadn't responded to my points in that new section.) Have a look at the bottom of #Noetica.27s_reply_to_M_3, I think that I responded to you quite 'reasonably'. I recall that we discerned 3 positions, and so, 2 conflicts. In your previous arguments, you seemed to support the "base constituents" view, but you wanted to keep the 'studies everything' view "open". I wanted that issue resolved. Your definition wasn't ignored. I responded to it in #Physics_as_a_super-science. "How can it be reasonable" that you didn't respond to the points made there? This seems to be the first time that you've provided an argument (citation) that went beyond "but physics is the study of everything". Good. Now, my response to your citations, and keep in mind that we're talking about our lead section:

"'In a sense' encompasses them" is a little less direct than I'd hope for. I think that this citation is focusing on the fact that physical laws are the basis for complex systems, but alright.
Chemistry can be seen as a subset of physics. Ok.
Very direct, as is 5, and to some extent 4.

Now, let me provide some citations for you on my position. I did not search explicitly for people who supported my position, instead, I looked for how respected sources defined physics. The 3 positions - matter and energy/force/etc. (M), base constituents or fundamental etc. (C), and all of nature (N) - are marked:

http://www.m-w.com/dictionary/physics (dictionary): M. "a science that deals with matter and energy and their interactions"
http://dictionary.reference.com/browse/physics (dictionaries): several dictionaries, all M
http://www.answers.com/main/ntquery?s=physics&gwp=13 (dictionaries, encyclopedias):
1. First dictionary has already been cited, 4 others all M.
2. McGraw-Hill: C. "Formerly called natural philosophy, physics is concerned with those aspects of nature which can be understood in a fundamental way in terms of elementary principles and laws. In the course of time, various specialized sciences broke away from physics to form autonomous fields of investigation. In this process physics retained its original aim of understanding the structure of the natural world and explaining natural phenomena."
3. Britannica concise: C. "Science that deals with the structure of matter and the interactions between the fundamental constituents of the observable universe. Long called natural philosophy (from the Greek physikos), physics is concerned with all aspects of nature, covering the behaviour of objects under the action of given forces and the nature and origin of gravitational, electromagnetic, and nuclear force fields. The goal of physics is to formulate comprehensive principles that bring together and explain all discernible phenomena."
4. Columbia: M. "physics, branch of science traditionally defined as the study of matter, energy, and the relation between them; it was called natural philosophy until the late 19th cent. and is still known by this name at a few universities. Physics is in some senses the oldest and most basic pure science; its discoveries find applications throughout the natural sciences, since matter and energy are the basic constituents of the natural world. The other sciences are generally more limited in their scope and may be considered branches that have split off from physics to become sciences in their own right."
Google search: encyclopedia
1. Columbia, again. http://www.encyclopedia.com/doc/1E1-physics-ent.html cites also:
  1. http://www.highbeam.com/doc/1P1-28750242.html canadian encyclopedia, M
2. (wikipedia)
3. Britannica, again.
4. http://encarta.msn.com/encyclopedia_761553206/Physics.html Encarta: C. "Physics, major science, dealing with the fundamental constituents of the universe, the forces they exert on one another, and the results produced by these forces. Sometimes in modern physics a more sophisticated approach is taken that incorporates elements of the three areas listed above; it relates to the laws of symmetry and conservation, such as those pertaining to energy, momentum, charge, and parity."
5. Columbia, again
Google search: define:physics. All relevant seem to support M.

What I gather from this is there is some dispute in the definition of physics. Some define it as dealing with specific things, matter and energy, as biology deals specifically with, say, earthly complex self-replicating organisms. Others define physics as a general (vague, in my opinion) "study of the fundamental", as biology might study "life". How do you propose we resolve this? I'd like you to answer some of the points I made above.

As for your definition, no, I don't like it. It's bloated and, frankly, ugly. It seems to resolve our dispute here by dumping it out into the article for readers to decipher. It's uncertain. And it's bloated. Compare:

Broadly, physics may best be thought of as the science of nature: the science concerned with identifying the basic constituents of the natural world, and the laws according to which they combine and interact to form complex systems. However, in most current everyday usage, physics is taken to be more limited, since there are special sciences (chemistry, biology, psychology, etc.) that deal with various kinds of complex systems using their own methods and theories. Physics is, for everyday practical purposes, the rest of science after these special sciences are taken out; and physics is the science that focuses more on the basic constituents and less on the complex systems that they form.

With:

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy

which is my proposed "consensus/wikipedic/truth-based" definition. If you wanted to resolve the dispute by dumping it out to the readers in an ugly way, you should have written:

Physics is the science concerned with the discovery and characterization of the fundamental constituents of nature, which are matter and energy, and of the universal laws which govern them.

–M^T 21:54, 2 November 2006 (UTC)

Noetica, M is not a physicist. He appears to be a protein specialist who enjoys the process of argumentation, and who has said that is how he learns. Thus this talk page is serving as a tutorial.

SFC9394, might it be time for a vote? -- Ancheta Wis 12:08, 2 November 2006 (UTC)

I'm about as far from a protien specialist as you are from being an author of children's books. Argument teaches one to think, interpret, and argue - these are the things I "learn" from it, and the reason I appreciate it. The extent to which I understand physics ("tutorial level", by your keen reckoning) has nothing to do with the arguments that I make. –M^T 21:54, 2 November 2006 (UTC)

Still pressing for a consensus (– Noetica)

M, I will respond to your last reply to me, above. I am no longer interested in sifting through the morass of diversions and obscurities from the last few days and weeks, and I will therefore not address the points you claim to have made at #Physics_as_a_super-science, just as you have refused to take notice of my direct challenges to you. Just one example. My point about Newtonian physics:

M argues that matter and energy are indeed acceptable, in the eyes of both physicists and the general public. But how can they be acceptable, if we want our definition to fit historically, and across cultures, and for all future developments? An early Newtonian working the same way might have characterised physics in terms of corpuscles and their interactions in real time and real Euclidean 3D-space. And that definition would, as we can now see clearly, fail on account of its restriction to the best available theory in Newton's time. What is wrong with appealing instead to the basic constituents of the natural world? Surely physics has always wanted to address these, whatever they turn out to be as a matter of empirical discovery or theoretical postulation.

Eventually, after I repeated the point and directly asked for your response, you "answered" with this:

My response to your newtonian point is a question: what are the "basic constituent of the natural world"? Atoms? Those 10000 distinct rules that certain parts of nature seem to abide by? Strings? Love? Waves? Equations? Ideas? Be specific! "Basic constituents" is meaningless to someone who doesn't quite understand what physicists think the world is made of.

I see this as an evasion, nothing more. You continually refuse to see the point that I make, no matter how often and how clearly I make it. What's more, other sources (some of which I cite above) are perfectly happy to use the term fundamental constituents, or equivalent. It is quite natural to keep things general in this way, to avoid tying a definition down to a particular time, place, or theoretical content. You simply refuse to allow this, without offering any worthwhile grounds for your refusal. From what evidence do you make your claim that people can't understand basic constituents, for heaven's sake?

I collect the points that I want to make, in summary form, in my last contribution above. Wasn't it obvious to you that I want editors to address that contribution, instead of having us all wade interminably back into the mountain of material that precedes?

You have now, for the first time, given your response to the definition I propose as I proposed it, instead of some straw man version. And what do you come up with? Just this:

As for your definition, no, I don't like it. It's bloated and, frankly, ugly. It seems to resolve our dispute here by dumping it out into the article for readers to decipher. It's uncertain. And it's bloated.

Bloated? We got that the first time. Now show me what is redundant in it, that bloats it? (Or better, answer that for the version below.) You understand the content, I think. So show us how you would express that content. Ugly? That's easy to say! Show us a more beautiful expression of that same content. And I deny that it "dumps" anything out into the article, for readers to "decipher". (Nicely chosen emotive terms, those!) Uncertain? It is as certain as it can properly be. Look, if physics is used in more than one sense, it is irresponsible for us to hide that fact, which is amply supported by my few citations from other encyclopedias and respected theorists. My proposal acknowledges this duality; it explains it; and (let me say it YET AGAIN, because you forever turn a blind eye to the fact) it INCLUDES the narrow definition that you favour! Can't get much more consensual than that. But we look in vain for concessions from you.

OK, here is a newly modified version that makes even more concessions:

Physics may be thought of broadly as the science of nature: the science concerned with identifying the basic constituents of the natural world, and the laws according to which they combine and interact to form complex systems. Normally physics is taken to be more limited, though, since there are special sciences (chemistry, biology, psychology, etc.) that deal more effectively with various kinds of complex systems, using their own methods and theories. Practically, physics is taken to be the rest of science after these special sciences are taken out: physics is concerned more with the basic constituents (currently using the concepts matter and energy), and less with the complex systems that are dealt with by the special sciences.

Now, where are your concessions? Or were you always completely persuaded that you were right, and deem yourself above the need to accommodate the well-argued views of others? If that's the case, I have only one remaining question for you: Why join a discussion aimed at consensus in the first place? – Noetica 23:37, 2 November 2006 (UTC)

I don't know what point you think I've been evading. I've given many responses to the one you quoted, asking "what's wrong with this". It's inconcrete. It avoids being informative for fear of being wrong - not wrong now, but some point in the future. It talks about the word 'physics', and not the contents of this article. And so on. When I do provide these arguments, you call them evasion, opinion, and so on, even when I cite other articles. I never argued against some "straw man" definition, but points that you brought up. As far as I can tell, you still claim that biology and psychology are just "physics applied to X". Should I agree to this? No. Should I ignore this? No, that seems to infuriate you. Should I argue against it? If I do, then I'm making up straw men!

If there's some conflict in the definition of physics, we should not worry so much about insulating ourselves from attack from either side in the lead section. We need a summary of what physics deals with. What's physics about? You offer a description of the conflict on this talk page, not a resolution, and surely not a summary definition. Physics isn't the sort of article that can afford that paragraph-long discussion in the lead. I proposed a somewhat shoddy alternative definition above, it was the very last thing I said to you. –M^T 01:03, 3 November 2006 (UTC)

Can I reply to M's last post by saying that dictionaries are hardly "respectable sources". Merriam-Webster (online dictionary) defines momentum as:

1 : a property of a moving body that the body has by virtue of its mass and motion and that is equal to the product of the body's mass and velocity; broadly : a property of a moving body that determines the length of time required to bring it to rest when under the action of a constant force or moment

2 : strength or force gained by motion or through the development of events,

of which the first sense is outdated by about a hundred years, and the second is laughable (momentum is a force gained through motion!). Encarta (online encyclopedia) is even worse in that it talks of conservation of this Newtonian momentum in relativity! However, I stopped looking in Encarta when I found this:

Electron, negatively charged particle found in an atom. Electrons, along with neutrons and protons, comprise the basic building blocks of all atoms. The electrons form the outer layer or layers of an atom, while the neutrons and protons make up the nucleus, or core, of the atom. Electrons, neutrons, and protons are elementary particles—that is, they are among the smallest parts of matter that scientists can isolate.

No prizes for spotting the sentence that almost reduced me to tears. Just to check how Encarta (online dictionary) defines an "elementary particle":

basic indivisible constituent of matter: any one of the subatomic constituents of which matter and energy are composed, e.g. electrons, leptons, photons, or hadrons.

What? A subatomic constituent of energy? Also, I must have missed the undergrad lecture in which they explained how hadrons were "elementary".

No, M, all you have cited are lay definitions that are, in all likelihood, created by well-meaning people with a rudimentary understanding of the subject.

From your last post, can I take it that you now accept that the broad definition is, in some general way, now acceptable? This marks a sudden change from numerous quotes of yours of the form "physics is not the study of nature", which, I might add, were never justified (bar trivial arguments of nomenclature).

I fail to see how, "Broadly, physics may best be thought of as the science of nature: the science concerned with identifying the basic constituents of the natural world, and the laws according to which they combine and interact to form complex systems." is vague. It is very clear in fact: physics is the study of nature. What is vague is what these "basic constituents," or "laws" are. But, then again, we wouldn't need physics if we knew what they were would we?

What dispute, exactly, does Noetica's definition "dump out" that the energy definition contained may I ask? "Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy" seems to address...nothing, really.

Lastly, how is this definition "consensus/wikipedic/truth" based? Consensus was never reached, I do not even know what you mean when you say it is wikipedic, and to speak of truth-based when talking about physics is very dangerous unless you are very careful: just what "truth" is it based on? Krea 00:09, 3 November 2006 (UTC)

Heh, I was making a play on Noetica's "Proposed consensus definition" (which I guess you didn't notice), the overuse of "consensus", and the implicit argument that because I'm not accepting Noetica's middle ground, that I must be against consensus. Yes, sometimes sources are outdated. Sometimes they oversimplify. Sometimes they're wrong. I'm sure that the sources quoted by Noetica in support have been wrong too (Encarta was one of those sources!). However, it's policy to hold sources in some regard. Higher regard than say, the word of a wikipedia editor. –M^T 01:03, 3 November 2006 (UTC)

Fair enough. But my point still stands that if you want to look up something about physics, you turn to a dictionary with trepidation. Noetica still has some very reputable citations; you don't: I still assert that your position that "physics is not the study of nature" is unjustified. I accept that I was at fault for not giving citations, but in my defense, it is generally an unspoken rule that physicists believe physics to applicable (in principle) to all of nature, which was why I was so surprised to see fellow physicists accept the energy definition and actually refute the broad one! You only have to go to physics department (and especially to a theory department because they generally have spent more time thinking about this stuff) and talk to a few people and this will be clear. Growing up learning physics, I acquired this impression subtly: it is inherent in the mindsets of the great physicists. Anyway, you may not like the broad definition, but do you now accept that it has a right to be in the article as at least an equal to any other definition, or do I need to scour my library? Krea 01:40, 3 November 2006 (UTC)

Krea and Noetica, I am attempting to build on your work. Let's make this happen. --Ancheta Wis 11:32, 3 November 2006 (UTC)

Great. But I am interested to hear back from M, and some previous editors who favoured the energy definition, such as MichaelMaggs. Krea 16:40, 3 November 2006 (UTC)

Thanks to SFC9394 for an excellent suggestion. Ancheta Wis, I watch with interest as your proposed lead develops. And I'm interested in yours too, Krea. I too am waiting to see what the "matter-and-energy" people will propose. I don't want to comment further until we have all proposals in. Meanwhile, I have offered my own proposal, though I may still alter it. – Noetica 04:47, 4 November 2006 (UTC)

I am saddened to see what has been happening here in the last few days. SFC9394's attempt to bring the discussion to a conclusion has been taken as an open invitation to re-state entrenched views as if the thousands of words of discussion above had simply not taken place. I had hoped we were converging to some sort of rough consensus with the wording we had thrashed out before - including both narrowphysics and broadphysics definitions - but editors now appear to have moved away from any real attempt to seek consensus. Civility has also been lacking in some cases. I fear that unless we re-establish the focus on consensus this will all turn out to be a monumental waste of time.--MichaelMaggs 07:58, 5 November 2006 (UTC)

Michael, SFC9394 has suggested that we post our proposals for the lead, and not comment too much right now. But I understood why you would want to make the observations you have. I am sorry that you can't discern any effort towards consensus in the last few days. I hope you will, when the time is right, let me know what in my proposal (and indeed in my latest definition, above) fails to respect the "narrow" view that I had opposed. Short of adopting that view, I can't for the life of me see how I could do more to accommodate it. But perhaps this is not the time. Let's follow SFC9394's suggestions, and wait until all the other proposals are in. Meanwhile, great to see yours, below. I am studying it carefully, along with the other proposals so far. As for civility, not attending to opposing views is a virulent form of incivility that can only breed further incivility. I hope we can all be attentive, but also restrained if we feel provoked. I for one intend to try! – Noetica 09:55, 5 November 2006 (UTC)

MichaelMaggs, it took a little bit of work, but I prepared the ground for the Carnap-Ramsey sentences which allow discussion without getting hung-up on names of things, sciences, objects, subjects, etc. This concept was taught explicitly to Feynman by his father (who was a uniforms salesman, but who in retrospect might also be called a natural philosopher). Hopefully this will lift up the level of discourse. --Ancheta Wis 13:10, 5 November 2006 (UTC)

Michael, I don't think anybody is re-stating entrenched views - such things never existed. You suggested a lead paragraph, it was opposed by some quarters, and we are now trying again. That is it. If you look at all the suggested lead sections below, I think that they all state the same key ideas - just with different emphasis. Therefore, how can you say that "editors now appear to have moved away from any real attempt to seek consensus"? Krea 14:38, 5 November 2006 (UTC)

Proposals

Physics series:;
	Physicists; Natural philosophy; Scientific revolution;
Topics in Physics
	Mechanics Classical mechanics; Quantum mechanics; ; Relativity; Electromagnetism; Thermodynamics; Statistical Mechanics; Fluid Mechanics; Mathematical Physics;
Major fields of Physics
	Astrophysics ; Atomic physics ; Condensed matter physics ; Molecular physics ; Nuclear physics ; Optics ; Particle physics ; Plasma physics;
	Physics Portal

Krea and Noetica,

My little experiment with <references/> has convinced me that you each cannot place separate citations in your own proposals, as I have the <references/> already.

--Ancheta Wis 13:15, 4 November 2006 (UTC)

Krea, I found an axiom system for physics which I referred to in an earlier thread. It is part of a set of axiom systems for languages, set theory and arithmetic, geometry, physics and biology. The physics axiom system actually describes the physics of a conversation, which I had appealed for in the talk page of another article, to which I had received no response. --Ancheta Wis 16:17, 5 November 2006 (UTC) The reference is

Rudolf Carnap (1958) Introduction to Symbolic Logic and Its Applications. New York: Dover Publications, Part Two, Chapter G, pp. 197-212.

Interesting. I'll pop down to the library to take a look today (if I can be bothered for the walk), or certainly tomorrow. Krea 17:27, 5 November 2006 (UTC)

MichaelMaggs, Energy and Information might very well become the canonical constructs for future syntheses in physics. My reasoning is that signalling has a good foundation in GR - see the citation above, so all that is necessary is to tie it to signalling in QM. --Ancheta Wis 16:17, 5 November 2006 (UTC)

I don't believe it will have escaped anyone reading my proposal that Physics has also studied the domain of the multiverse in the past 5 decades, which finesses the nature vs matter/energy talk stream we have been witnessing. --Ancheta Wis 23:40, 5 November 2006 (UTC)

SFC9394, Complex systems are also part of physics, and not just biology etc. Would anyone object if I placed a writeup in my section 5 about this. I recognize that this is premature, and can wait. --Ancheta Wis 13:32, 4 November 2006 (UTC)

Focus

Ok - here is what I propose. For anyone who wants to (be they a long time contributor to this page or someone who hasn't posted anything) I invite them to post a 200-400 word lead section. This is all that I ask for - no discussions - not critiquing what someone else has proposed - just the lead section you want. The format should be:

A separator line, ----

A header line of "Username's lead proposal: "

A blank line,

The text that you want as the leading section, formatted as you wish,

A second separator line ---- to ensure each proposal is properly contained.

If you don't wish to submit a proposal then that is fine. A straw poll will be taken on what is received. The straw poll won't be a vote, and the outcome of it won't decide what the lead text is. What it will allow us all to do is to focus on the specifics. I posted my comments (~400 words) 25 hours ago - and this page has racked up ~4,000 words of response in that short time. Great if they were new words, but it is just chasing tail stuff once again. If folks won't focus voluntarily then I will attempt to do it by this method of asking for a lead text proposal from all parties. I suggest around a week or so for submissions to be accepted - that is flexible if editors have reasons for requiring a longer amount of time.

I fail to see the point of opening up the WIP page to open editing - all that will do is transfer the debate on here to edit wars on there - it will also have the confusion of not allowing proper and "clear" discussion. ie. Two people disagree over whether the physics knowledge tree should be represented in prose style or tabular style - they will struggle to generate a visible discussion on this talk page if we have thousands of words being traded in heated debates over the lead section. Also those involved in the heated debates are not going to have as much (if any) time to get involved on which way the knowledge tree should be presented – we have few enough editors involved in this process as it is – splitting our numbers further would be of great detriment. In short, the process would become a carbon copy of the mess that was the main talk page/article - i.e. a talk page with 20 voices discussing 5 topics simultaneously - and an article page having 20 participants in edit wars on 5 pieces of detail simultaneously.

I submit the above proposal to other editors - focus is required - the past 25 hours have confirmed in my mind that without it this is just going to become nothing but people going around in circles. SFC9394 23:56, 2 November 2006 (UTC)
----
===~~~'s lead proposal, ~~~~~===
Your proposal here
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Ok, this is what I have quickly come up with... Krea 01:12, 3 November 2006 (UTC)

Krea's lead proposal, 01:12, 3 November 2006 (UTC)

Physics is the process by which one aims to obtain knowledge of nature: it tries to discover and understand the basic constituents of nature and their interactions through a framework called the scientific method.

Throughout history, the difficulty of this task meant that, at any one particular time, physics often had to focus its enquiry on some specific aspect of nature on which reasonable progress could be made. Thus, physics is often regarded as a science separate from the other traditional sciences (such as chemistry, biology etc.), which only aims to talk about those aspects of nature not covered by these fields - even though it can be, and often is, regarded to be their progenitor. Therefore, it is often heard that physics is the study of matter and energy, forces and motion, or some combination of these concepts, even though it is widely regarded that the true domain of physics is, in fact, not bounded by such concepts.

Ancheta Wis's lead proposal, 01:44, 3 November 2006 (UTC)

An example of the system of the world: -- looking to the west, clouds are moving toward us, in an illustration of the rotation of the Earth. The clouds are part of an atmosphere with a uniform temperature across the sky at a single altitude, but with temperature which varies with altitude. The clouds have condensed from vapor to water droplet at a precise temperature, uniformly, thus causing a **flat-bottomed cloud**. The air is not mixing at these altitudes, which we see as a straight line, parallel to the horizon. Thus **gravitation is influencing the shape of the flat-bottomed clouds**. At other locations in the sky, the clouds are subject to turbulence and mixing. The density of the atmosphere also is varying with altitude, causing a continuum of hue, with deeper blue at the zenith and lighter blue at the horizon (obscured by the trees). The blue color of the sky is due to Rayleigh scattering, which also explains the red color of the sunsets (not shown).

1. Definition

Physics (from the Greek, φύσις (phúsis), "nature" and φυσική (phusiké), "knowledge of nature") may be thought of broadly as the science of nature:^[1] the science concerned with identifying the constituents of the natural world,^[2] and the laws according to which they combine and interact^[3] to form complex systems.

Other sciences (chemistry, biology, psychology, etc.) study specialized kinds of complex systems, using their own methods and theories, although, historically, physics is subsuming the infrastructure,^[4],^[5] ^[6] upon which those sciences are built. Currently the basic concepts used by the other sciences include matter and energy;^[7] the complex systems that are dealt with by the special sciences increasingly use models built up from physics, as well as from their own history of development.

Physics need not be considered an arcane or difficult subject. Classical mechanics can be amply illustrated on children's playground equipment or in a sports stadium. Read on to view another type of sport --

Note to the reader: You may, without loss of generality, skip any point marked by a bullet below, e.g.

This denotes a detail.

2. Introduction

The basic program for physics was instituted most noticeably by the time of the scientific revolution. In this program, a 'system of the world' was demonstrated by Newton,^[8] by which ever simpler constructs could be examined. This was the basis for several revolutions over the succeeding centuries during which physics became more and more exact and also more and more abstract. The program for mechanics, instituted by Newton, basically answered 'where' and 'when'.^[9] This was the triumph of the geometrization of mechanics begun by Galileo.

Cassiopeia A - a spherically symmetric remnant of the 1680 supernova

File:PrismAndLight.jpg

Diffraction of light by a prism.

Experiment. Historically, physics has developed hand-in-hand with technology; the experimental devices of the scientists of each era had features which were consistent with the physics of that time. For example,

Walter Bothe built the AND gate for a coincidence detector for use in Compton scattering. For this work he got the Nobel prize, 30 years later, in 1954. Today, Boolean logic is routinely used in engineering and information technology.
Galileo built his own telescope (but not the lenses) - philosopher Baruch Spinoza was a lens grinder.
Isaac Newton, accounted the greatest physicist in history, built his own telescopes by grinding his own mirrors with pitch (from which we routinely use Newton's rings to judge the quality of a telescope's mirror), and performed his own optical and alchemical experiments.
The following list of technology which has been used in experiments can serve as a chronicle for the history of experimentation, as applied in an experiment (sorted by date of invention)

4500 BCE - the astronomical observatory is ancient enough for observations in India to document the precession of the constellations,

2700 BCE - a simple machine - the inclined plane - used by Galileo to determine the acceleration of gravity in the early 1600s,

2000 BCE - mirrors were exploited by Isaac Newton to minimize the abberation in the telescope in the 1670s,

300 BCE - the pump was used by Otto von Guericke to produce a vacuum in 1654,

200 BCE - the astrolabe was used in navigation,

80 BCE - the gear was used in the engine,

975 - the pendulum was used by Galileo to measure time,

1280 - the lens was used to build telescopes,

1600 - the telescope was used by Ole Rømer to measure the speed of light by observing the motion of Io across Jupiter,

1680 - a prism was used by Newton to determine a theory of light,

1700 - the bell jar was used to study vacuum and the atmosphere,

1745 - the Leyden jar was used to store electrical charge,

1761 - the chronometer was used to measure time at sea,

1824 - the engine was used to provide energy and do work,

1821 - a railroad car was crucial for the development of relativity,

1860 - the spectroscope was to be used in quantum theory,

1903 - the airplane has been used to measure the cosmic microwave background,

1906 - the vacuum tube was used as an electrical circuit element,

1924 - Walter Bothe builds the AND gate, an electrical circuit element, as a coincidence detector for use in Compton scattering in 1924,

1929 - the cyclotron was used to accelerate charged particles,

1935 - the magnetron was built as a source of microwave radiation (suitable for radio frequency direction finding and a crucial element of the technology disclosed by the British to the Americans on the eve of WWII),

1945 - the digital computer was used to solve equations,

1947 - the transistor was used as a circuit element,

1957 - Isaac Newton proposed a thought experiment for a artificial satellite as part of his demonstration of the free-fall of the planets (1687),

1959 - the integrated circuit could miniaturize and commoditize circuits,

1960 - the laser was built as a source of photons,

1969 - the internet could commoditize knowledge,

1978 - the global positioning system of artificial satellites could commoditize the determination of position and time,

1986 - the atomic force microscope could manipulate atoms,

1999 - NIST-F1 could serve as a time standard

etc.

The hands-on experience with the devices of technology is an essential part of physics. Richard Feynman, blunt-spoken and not known for diplomacy, once remarked that the 1930's era cyclotron at MIT was hand-built and well-used, while the cyclotron at Princeton, was more professionally built, and therefore little-used during his term of study there. Forty years later, building cyclotrons was a high-school level activity, which can cause signficant drain on the electrical grid of the neighborhood.
Physicists have used the technology of each era to further their own scientific predictions, as well as to further the development of mathematics, in each era, in a cooperative effort.

Theory. Step by step, the constructs took basic mathematical models of physicists -- Galileo, Newton, Lagrange, Hamilton, Faraday, Maxwell, Boltzmann, Gibbs, Planck, Einstein, Bohr, Dirac, and others and applied them with ever greater precision.

The interplay between theory and the real world (as experimentalists like to say) has been fruitful for physics:
- new physical phenomena can serve as challenges to theoreticians to be explained in their theories because that theory is incomplete, or
- to show that a hypothesis has been disproved and the theoretician must select another realm of possibility, or
- a theory has been corroborated -- and the theory is not yet disproven.
The thought experiment need not be expensive, but the people who are able to create them are required, for their publication.
One technique used in physics research involves Carnap-Ramsey sentences. The free and bold construction of mental models has existed from the inception of the science of physics; this technique shows specifically how to side-step questions of ontology by focusing on the gist rather on potentially irrelevant detail: "every time a theoretical term appears in a theory one should substitute a variable x for it and the theory should be preceded by the expression 'there exists a certain thing x, such that ... '".^[10]
- For example, a brane can be fruitfully applied in this way, without worry whether branes 'exist' -- thus Henry Tye can theorize that the Big Bang was produced by the collision of a brane and its anti-brane, which is a statement that would apply before the emergence of spacetime.
- This free mode of thought can be used, for example to solve any differential equation (as Feynman liked to put it^[11]), but it requires imagination.

Today, even the most basic concepts such as space and time are known to their theoretical limits; in physics we can even conceive of a smallest space and a smallest time which are known to be nonzero. Today, experimentation has progressed to the point that single atoms can be imaged in their positions in materials, and single atoms can be positioned at will, where earlier physicists from two thousand years before could only speculate on the existence of atoms on the grounds of ontology. Although it takes enormous amounts of energy (i.e., money), particles can even be artificially created or destroyed.

But the mass points of Newton are now the target for even closer scrutiny and require the consideration of stupefyingly high-energy realms which we cannot investigate experimentally on Earth, leaving us only the cosmos as our laboratory for particle physics. What are under investigation are basic properties of the Standard Model and the symmetry exposed by the model. The process of development in physics continues to this day, with no limits in sight.

Prerequisites
scientific notation
natural units
algebra
geometry
vector notation
optics
operators
differential equations
partial differential equations
mechanical engineering
electrical engineering
probability
statistics

3. History & Foundations

4. Principles/Concepts

5. Current Topics/Current Research

6. Applications and Influence

7. References and Notes

^ "Greek Physics", in "Physical Sciences, History of" Encyclopædia Britannica, 15th ed.
^ "Physics", Encyclopædia Britannica, 15th ed.
^ "Physical Theories, Mathematical Aspects of", Encyclopædia Britannica, 15th ed.
^ For chemistry, the periodic table of the elements can be explained directly by quantum mechanics
^ For biology, the discovery of the structure of DNA was made by concrete modelling, based on x-ray diffraction experiments. Based on this result, Francis Crick immediately noted its significance for the explanation of life.
^ For psychology, the time-sequenced operation of the visual system is predicated on the action of mirror neurons, which anticipate actions of the subjects in view. Jeff Hawkins predicted this one year (2004) before experimental confirmation (2005) by Giacomo Rizzolatti, Leonardo Fogassi, Vittorio Galles. "Mirrors in the Mind", Scientific American November 2006, pp.54-61.
^ See for example, "Physics", Columbia Encyclopedia
^ Newton (1687) Philosophiae Naturalis Principia Mathematica
^ Richard Feynman (1963) The Feynman Lectures on Physics 1 p.5-1.
^ G. Toraldo di Francia (1976), The Investigation of the Physical World ISBN 0-521-29925-X p.74
^ Laurie M. Brown, Feynman's [Ph.D.] Thesis: A new approach to Quantum Theory ISBN 981-256-366-0 p.13

8. External Links

Noetica's proposal (Lead and Introduction, combined) – Noetica 04:31, 4 November 2006 (UTC)

File:Holding flower.jpg

Everything in the universe, large and small, is within the domain of physics.

Physics is the scientific study of nature. Broadly, it aims to identify the basic constituents of the natural world and the laws according to which they combine and interact in complex systems. This is how physics is best understood philosophically, and throughout much of its history – especially as it developed in ancient Greece. The word itself is straightforwardly derived from Greek: τα φυσικά (ta phusiká), "[the study of] the things of nature", connected with the word φύσις (phúsis), "nature".

In modern times, however, and for practical purposes, physics is usually understood in a more narrow sense. There are special sciences to deal most efficiently with certain kinds of complex systems: chemistry with reactions among elements and compounds, biology with living organisms, neuroscience with nervous systems, and so on. Each of these special sciences adds its own concepts, theories, and methods to the general stock that is available for all of science.

Physics, therefore, is usually understood to be the rest of science after the special sciences are taken out: it is concerned more with basic constituents, and less with complex systems. For most of the present article this narrow understanding of physics will be assumed. The article will deal with physics as it is conceived of, and practised, by contemporary physicists.

Even narrowed in this way, physics retains a central place among the sciences. As W.V.O. Quine puts it: "If the physicist suspected there was any event that did not consist in a redistribution of the elementary states allowed for by his physical theory, he would seek a way of supplementing his theory. Full coverage in this sense is the very business of physics, and only of physics" (Theories and things, 1981, p. 99). Because the reach of physics remains so broad and universal, the work of physicists stimulates and inspires progress in other sciences. Quite probably, theoretical work by the Nobel-laureate physicist Erwin Schrödinger (in What is Life?, 1944) ultimately enabled the discovery of DNA by Francis Crick and James Watson. And this momentous discovery in molecular biology, with all of its implications for the life sciences, was achieved in a physics laboratory: the Cavendish.

Contemporary physics has evolved these core features:

1. Like all contemporary science, physics is a strongly empirical form of inquiry, using experimentation to test its theories.

2. Most theory in physics relies heavily on mathematical modelling.

3. Physics treats as fundamental two pairs of concepts:

matter and energy
space and time

4. Physics is conventionally divided into:

classical physics (from the work of Isaac Newton, up to and including relativity)
modern physics (essentially the same as quantum mechanics and its derivatives)

5. Physics is also divided into:

MichaelMaggs's lead proposal, 08:13, 5 November 2006 (UTC)

Physics is the science concerned with the discovery and characterization of the universal laws which govern matter and energy. Physicists formulate these laws as mathematical theories which attempt to model the behaviour of physical systems at some perceived fundamental level. The aim, however, is to go beyond describing physical phenomena, and to construct theories which can also predict how a physical system will behave. These predictions can then be tested experimentally to verify or falsify the theory.

Some theories are of such significance that they are referred to as the laws of physics. Typically, these are physical principles that are believed to be common to all physical systems, or at least are of very general applicability. Some principles, such as Newton's laws of motion, are still generally called "laws" even though they are now known not to be of such universal applicability as was once thought. The word 'law' is a misnomer since even a law of physics could, in principle, be disproved by experiment. Other theories are more limited: they describe the behaviour of specific physical systems only, or are applicable only under certain circumstances.

Since one of the major goals of physics is the formulation of theories of universal applicability, on a broad perspective physics can be viewed as the study of those univeral laws which define, at the most fundamental level possible, the behaviour of the physical universe.

Classical physics traditionally includes the fields of mechanics, optics, electricity, magnetism, acoustics and heat. The more recent fields of general and special relativity are also usually placed within this category. Modern Physics is a term normally used to cover fields which rely on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics and condensed matter physics. Although this distinction can be commonly found in older writings, it is of limited current significance as quantum effects are now understood to be of importance even in fields previously considered purely classical.

Physics research is divided into two main branches: experimental physics and theoretical physics. Experimental physics focuses mainly on empirical research, and on the development and testing of theories against practical experiment. Theoretical physics is more closely related to mathematics, and involves generating and working through the mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available.

Some comments on the definition of physics

I came over here in response to a posting on the WikiProject:Physics page. I have to say that I'm a bit disappointed by this fight going on in defining physics. I haven't read all of the thousands of words of comments above but I hope I've read enough to perhaps add a few helpful comments of my own.

As a theoretical physicist, I'm sympathetic with the "physics is the study of nature" sentiment. But I do think this definition is unhelpful for the general reader who wants to know more specifically what physicists do and/or think about. This is much more limited than "all of nature". For example, it would be foolish to suggest that the animal behavioralist, who goes out and films cheetahs or whatnot, is doing physics. It's true that the running and jumping of the cheetah is governed by Newtonian mechanics and that the animal's biochemistry is a complicated quantum mechanical system. But these concepts are not terribly useful in describing that area of nature. And the people who do this kind of science are not, by any stretch of the imagination, physicists.

Now, physics is an extremely broad field, which is why it's hard to pin down. While it doesn't accept any real limitations to its realm of validity, in practice physicists by and large study a reasonable short list of phenomena which no other field really addresses. A good starting point would be to simply list the things that one learns about while earning an undergraduate physics degree: motion/dynamics/statics; electromagnetism and light; atomic and sub-atomic phenomena( i.e. particle physics, nuclear physics, radiactivity); gravitation and spacetime; cosmology and astrophysics; the electrical, mechanical, and optical properties of bulk matter; thermodynamics and statistical mechanics. To be sure, there are physicists who do other things, for instance, biophysics, chemical physics, and complex systems, but these aren't really the core of the field.

So I guess my main point is we should try to describe physics as a scientific field determined by the areas of study of its practitioners, not some overaching philosophical view. I apologize if this has been stated before but I didn't have the patience to read the entire talk page. Joshua Davis 04:15, 6 November 2006

Commentary appended Ancheta Wis 14:30, 9 November 2006 (UTC)

I came over here in response to a posting on the WikiProject:Physics page. I have to say that I'm a bit disappointed by this fight going on in defining physics. I haven't read all of the thousands of words of comments above but I hope I've read enough to perhaps add a few helpful comments of my own.

As a theoretical physicist, I'm sympathetic with the "physics is the study of nature" sentiment. But I do think this definition is unhelpful for the general reader who wants to know more specifically what physicists do and/or think about. This is much more limited than "all of nature". For example, it would be foolish to suggest that the animal behavioralist, who goes out and films cheetahs or whatnot, is doing physics. It's true that the running and jumping of the cheetah is governed by Newtonian mechanics and that the animal's biochemistry is a complicated quantum mechanical system. But these concepts are not terribly useful in describing that area of nature. And the people who do this kind of science are not, by any stretch of the imagination, physicists.

Now, physics is an extremely broad field, which is why it's hard to pin down. While it doesn't accept any real limitations to its realm of validity, in practice physicists by and large study a reasonable short list of phenomena which no other field really addresses. A good starting point would be to simply list the things that one learns about while earning an undergraduate physics degree: motion/dynamics/statics; electromagnetism and light; atomic and sub-atomic phenomena( i.e. particle physics, nuclear physics, radiactivity); gravitation and spacetime; cosmology and astrophysics; the electrical, mechanical, and optical properties of bulk matter; thermodynamics and statistical mechanics. To be sure, there are physicists who do other things, for instance, biophysics, chemical physics, and complex systems, but these aren't really the core of the field.

So I guess my main point is we should try to describe physics as a scientific field determined by the areas of study of its practitioners, not some overaching philosophical view. I apologize if this has been stated before but I didn't have the patience to read the entire talk page. Joshua Davis 04:15, 6 November 2006 (UTC)

It should be clear that the page needs active moderators. I archived the hundreds of KB for the benefit of those who will have come after you. In the meantime, your points will be appreciated. Now, in behalf of SFC9394, might I ask that you contribute some moderation and/or content for this page. Speaking for the prior contributors, --Ancheta Wis 06:17, 6 November 2006 (UTC)

Newton left an admonition about a theory of everything:

"To explain all nature is too difficult a task for any one man or even for any one age. 'Tis much better to do a little with certainty, and leave the rest for others that come after you, than to explain all things."

Thinking about it, I am disturbed that an aggregate definition might be acceptable. This is similar to the situation on the matter page, which after all is one of the components of one of the mooted definitions. This is not a theoretical discussion. The composition of concrete is aggregate, and the success and integrity of a building foundation has everything to do with the material of which the the building is made. Thus, the Pantheon of Rome survives, because its concrete was made of volcanic material, and not of sediment, which will degrade more rapidly, as the materials have less of a crystalline structure. How might one seriously build a structure for the ages? i.e. Physics. --Ancheta Wis 08:10, 6 November 2006 (UTC)

Back to the cheetahs. At Wikimania 2006, we were privileged to visit the MIT Museum, which is mainly about robotics. There were the stroboscopic pictures of Edgerton, including the stream of water, and the bullet thru the apple, and the A-bomb. And indeed, there were robotic mechanical devices which jump like kangaroos, and roll, etc. And there were pieces of plumbing which wriggled like snakes, etc. The engineers of MIT are seriously embarking on the cognitive end as well. So we cannot be so sure that deterministic renditions of anything on the planet cannot be described or built. Now my personal reaction to the herds of robotic kangaroos jumping was depression. I know there is more to Nature than that. Now Newton described himself as a child on the seashore of the Ocean of Truth, vis a vis Newtons' quotation above. But an Ocean of Knowledge is an exact forebear of this encyclopedia. Come on. Let's get this going. Even a provisional or aggregate definition is better than 300,00 KB of argumentation. --Ancheta Wis 12:09, 6 November 2006 (UTC)

I suppose I really should wait for the 1-week-deadline to pass before making comments, but I doubt anybody else will put forward a definition, so I'll just say this: expanding on what Joshua has said (and I hope that he, or anybody else for that matter, sticks around), there are two issues that need to be addressed. We need to define what physics is, and explain what it is that physicists do. These are two, related yet, different things. To me, with the former, there is no issue: physics is the study of nature. Period. Any statement that says that physics is defined as the study of matter and energy will have to be justified in order for myself to yield. Why am I so unequivocal? I have never heard any reputable source define physics so, whereas I have encountered, and read the broad definition countless times. Is this what physicists actually do? Of course not. We all know that. What we do is indeed study matter and energy, or this or that, and not the whole of nature. We could also go down Joshua's suggestion of listing the fields of study (messy in my opinion). My point is that let's not mix the two issues. Krea 15:00, 6 November 2006 (UTC)

I think we need to focus on the what the article is supposed to get across to people. It isn't very clear to say "physics is the scientific study nature". Science is the scientific study of nature. I'm sympathetic with the notion that everything in nature obeys the laws of physics while not everything obeys the laws of, say, biology. Physics is all-encompassing in that way. But If someone tells me that they're a physicist, I can safely deduce that they don't study animal behavior. You can get into a big to-do that animal behavior is really determined by basic principles of physics at the fundamental level, but if you get too philosophical, you're in danger of violating NPOV. The point is that "physics is what physicists do" is probably the best definition, really. But let me suggest something a little more eloquent for an opener: "Physics is a broad field of inquiry into the natural world, that provides foundational elements for the other natural sciences. Although practicing physicists traditionally study a limited (albeit rather broad) set of phenomena, the principles of physics are applicable throughout natural science." Then some example about how your circulatory system obeys hydrodynamics and how chemistry is complicated quantum mechanics. Then go go on to list the traditional areas of physics but then point out that there are people who do the physics of biology, geology, information systems, blah, blah, blah. The main points to get across are that physics is really broad(from sub-atomic to extra-galactic); it's principles apply throughout natural science; traditionally physicists study the things in the list I made above; there are physicists in other disciplnes as well(this is connected to the second point). I think this gives the field sufficient credit without getting into metaphysics. Joshua Davis 18:29, 6 November 2006 (UTC)

Yup, that's pretty much either what I've already said, or agree with. Saying "physics is the study of nature" (or something similar) may confuse some people, but it simply has to be there, and with prominence (with explanations if need be). For issues of clarity, I don't mind adding suspect (at least to me) lines like "physics is the study of matter and energy", as long as it is stated that this merely for purposes of clarity and is not a widely held definition of the subject. The issue that surrounded this discussion was that some people felt that the broad definition of physics (that it was the study of nature) was either incorrect, or not worthy of any place in the lead paragraph. I am really waiting for these people to restate their position and argue for their point. Krea 20:25, 6 November 2006 (UTC)

Krea, I can finally propose a sharper set of definitions:

Physics searches for new knowledge of nature.
Physicists are all of those who have discovered new physics.
Science is systematized knowledge.
Scientists are those researchers who have contributed to science (new or not), its study and systematization.
Scientific method is that method by which scientists prove and improve their science.
Technology is the application of science to the solution of some problem.
Engineers or technologists are all those who use a technology to solve some problem.

Frankly, I do not expect anyone to subscribe to these definitions as they define a rather elite group as physicists, and this would raise an outcry by those who have not yet discovered new science, but who still consider themselves X, Y, or Z. But by this definition, any experimentalist who has discovered a new effect, or any theoretician who has predicted a hitherto unknown effect, and who is vindicated, could be called a physicist. This would define Jeff Hawkins and the researchers on mirror neurons as physicists, as this is brand-new knowledge. This puts scientific method at the center of Science. For example, this would clearly define Medicine as a Science, and recognize any physician who has correctly diagnosed a disease as a scientist. But any physician who merely follows some medical practice by rote, without the use of diagnosis, would be a technologist. A technologist, for example all those who work on computers, by definition is a problem solver and thus also a productive member of society. What am I getting at? The viewpoint that physics takes imagination and comprehension of the highest order.

I retain the previous definition in my proposal. --Ancheta Wis 01:00, 8 November 2006 (UTC)

Sorry Ancheta but do you think that physicists are only those who discovered some new physics? because in that case there we'll be just a few physicists around the world today... Physicists in my opinion are those who research in the fields of physics... Tatonzolo 08:07, 8 November 2006 (UTC)

No need to apologize. There can only a few when the science requires so much. And you are free to your own definition; just state it and let's move on. Logic and reason will out. --Ancheta Wis 12:56, 8 November 2006 (UTC)

Ancheta, I think your points above really make clear why a broad definition of physics is... difficult... If I discover some hitherto unknow detail about the mating habits of African swallows, this would qualify as new knowledge of nature. By your definition it seems to me that this would make me a physicist, and my paper on this new discovery should be published in a physics journal (it's physics, isn't it??). From the arguments presented in this discussion the past several weeks, I have a real problem in understanding why not all biologists, chemists or whatever should be called physicists. O. Prytz 21:38, 8 November 2006 (UTC)

You are missing my point. Crows are amazingly smart birds. I am not so sure about African swallows. Crows can count. Child crows visit their mothers. There is something going on there that I am not sure is so true about African swallows. The point is surprise. Good science is surprising as well as true and valid and robust and observable etc. If you are able to convince a physics editor you have made a contribution to the science, then, guess what? Previously, I mentioned that one of my teachers was curious about some rocks he found in his desk. He investigated and got his result published in a physics journal. The previous discussion agreed that he can be considered a physicist, and not only an electrical engineer, because he is one of the founders of the integrated circuit industry. By the way, my teacher's paper showed the equations behind the solar cell, so he ought to be a billionaire from the royalties, but he isn't. --Ancheta Wis 22:14, 8 November 2006 (UTC)

I can appreciate the difficulty of the broad definition - really, I can. It can be hard definition to swallow (excuse the pun), but that really boils down familiarity. If you were taught that "physics is the study of nature" from a young age, would you really find it so problematic? The answer is no, probably not.

Yes, technically, under this definition, physics is the only science: biology and chemistry and any other field is merely a sub-field of physics, like thermodynamics or gravitation, for example. But, why is this hard to comprehend? Is it because you consider biologists to study objects separate from the physical world (in the Cartesian dualistic sense), or that it goes against your childhood education that taught you that physics was about matter and forces, biology was about life... If it is the former, then that deserves more enquirey, but if it is the latter, then you are worrying about trivial things.

Let me try to be a little clearer: why shouldn't biology (that's the field I've decided to pick on!) be considered a sub-field of physics? If you can come up with an answer that appeals to some physical observation of nature, then I really would be interested in hearing it. If you can only appeal to statements like, "well, it doesn't seem right," then your argument is "trivial".

O. Prytz, the cold-blooded answer is: under this definition, yes, you are a physicist. Thats just feels wrong though, doesn't it? But why? I argue that it feels wrong, not because of any real "physical" reason but, because it goes against what we were taught to believe as kids: it's a fundamental shock to our notions of what we thought the various sciences were.

There are many reasons why we, in a colloquial sense, regard biology to be separate from a lay understanding of what physics is. One of them is that we actually give these fields a lot more respect than the broad defintion gives them. But that doesn't change the fact that there is nothing wrong or contradictory about the broad definition.

Concerning the issue of comprehensibility (which seems appropriate right now): will the average reader appreciate all of this? Well, it's our duty to try, instead of abandoning interesting arguments (that aren't original to editor, in the wikipedia philosophy) for dumbed-down explanations.

To Ancheta: my definitions would be:

Physics is the search for knowledge of nature.
Physicists are those people who search for knowledge of nature.
Science is any study that implements the scientific method.
Scientists are those people who engage in Science as defined above.

The definitions are just a personal things though, as you mention. Personally, I define physicists such that even those "robots" amongst us who just re-apply known methods to achieve some result, are called physicists too (although you can argue that they're not good physicists!). On a technical note, my definitions would mean that engineers/technologists are physicists too, right? Anyway, these definitions probably result from my personal hatred of "elitism" though... Krea 00:34, 9 November 2006 (UTC)

To Ancheta, here are my possibile definitions:

Physics is the science involved in understanding nature
Physicists are those researching in one or more fields of physics
Science is any study that implements the scientific method (I agree with Krea on this)
Scientists are those people who research in one or more scientific fields.

Tatonzolo 09:10, 9 November 2006 (UTC)

Despite how much I enjoy and am amused by how this latest round of argument - "biology is physics!" - is helping my position, I really would like you us to take that rest that I thought we had agreed to take, and let the head clear. Perhaps prepare a concise statement of your position and arguments, to be posted as we did the leads? You're not even responding to points anymore, you're just emphasizing the exact same position you stated in the previous post, with different but similar examples and explanations. –M^T 10:02, 9 November 2006 (UTC)

I agree. SFC9394, as moderator, has asked us to stop these fruitless discussions and simply post our proposals for lead paragraphs. If anything useful is to come out of this it's essential that we follow SFC9394's guidance, as we agreed to do at the very start, and to avoid the temptation to allow enthusiasm for our own positions to carry us away. I'm drawing a double line here, and I suggest no further argument whatsoever until SFC9394 tells us how he wants us to proceed--MichaelMaggs 10:28, 9 November 2006 (UTC)

Fair enough. I wasn't making any definitive statements that would settle the argument: I was just replying to O. Prytz through a commentary about the situation as seen through my perspective (which you could argue just contradicts the first clause of that sentence). M, if you want a concise statement of my position and arguments, how about: why can't I say "biology is physics"? (Although it's not much of an "argument", and I suggest it with no lack of respect for biologists). Again, I don't expect anyone to reply, but just to think about it. Krea 11:20, 9 November 2006 (UTC)

makenzi

it means dat im da best yes mariam adalat is da best u get wat im sayin

.R.E.S.P.E.C.T.

[1] "Greek Physics", in "Physical Sciences, History of" Encyclopædia Britannica, 15th ed.

[2] "Physics", Encyclopædia Britannica, 15th ed.

[3] "Physical Theories, Mathematical Aspects of", Encyclopædia Britannica, 15th ed.

[4] For chemistry, the periodic table of the elements can be explained directly by quantum mechanics

[5] For biology, the discovery of the structure of DNA was made by concrete modelling, based on x-ray diffraction experiments. Based on this result, Francis Crick immediately noted its significance for the explanation of life.

[6] For psychology, the time-sequenced operation of the visual system is predicated on the action of mirror neurons, which anticipate actions of the subjects in view. Jeff Hawkins predicted this one year (2004) before experimental confirmation (2005) by Giacomo Rizzolatti, Leonardo Fogassi, Vittorio Galles. "Mirrors in the Mind", Scientific American November 2006, pp.54-61.

[7] See for example, "Physics", Columbia Encyclopedia

[8] Newton (1687) Philosophiae Naturalis Principia Mathematica

[9] Richard Feynman (1963) The Feynman Lectures on Physics 1 p.5-1.

[10] G. Toraldo di Francia (1976), The Investigation of the Physical World ISBN 0-521-29925-X p.74

[11] Laurie M. Brown, Feynman's [Ph.D.] Thesis: A new approach to Quantum Theory ISBN 981-256-366-0 p.13

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