User talk:Edgerck/Comments Reliance On Information 1

If you have comments on this experiment, please leave your message in the talk page.

Comments On Reliance On Information Experiment 1

DISCLAIMER: THIS IS NOT INTENDED TO BE A CRITICISM OF WP. IT IS INTENDED TO POSITIVELY CONTRIBUTE TO THE UNDERSTANDING OF THE DYNAMICS OF INFORMATION RELIANCE IN GENERAL AND WP RELIANCE IN PARTICULAR, WITHIN THE LIMITATIONS OF THE PRESENT STATE OF WP TECHNOLOGY AND USER RULES.

(MY COMMENTS ARE IN GRAY, INLINED, LEFT FLUSHED. THANK YOU FOR YOUR PARTICIPATION!)

You might like to have a look at Criticism of Wikipedia, Wikipedia:Wikipedia is failing and numerious other essay and articles on the topic. Indeed it might work better as a sub page rather as part of your talk page. If you want some more comments consider anouncing it on WP:VPM. --Salix alba (talk) 12:36, 22 May 2007 (UTC)

Thanks. I just added a DISCLAIMER saying that this experiment is not a criticism. I don't even know what the result will be and how it compares with other sources (Britannica, for example). I will announce it at WP:VPM. BTW, I added a reference to the previous work you mentioned. I may turn this into a WP-essay when the experiment reaches some intermediate maturity time. Edgerck 18:41, 22 May 2007 (UTC)

Interesting experiment! Do you have more precise decay statistics from the first round?

Not precise, just indicative of decay -- and disappearance of correct information.

As an aside, I think your vector cross product example might not be quite as indisputable as you suggest. I'm writing this from a mathematician's viewpoint, and what I detect is an apparent difference of usage in maths and (at least a part of) physics. You state strongly that the cross product of two vectors in R³ is not a vector but instead a "pseudovector". However, for this statement to make sense, one cannot use the usual definition of a vector in mathematics as simply an element in a vector space (a finite dimnsional real one with a metric (or Hodge star) for cross products), but must use a definition that relies on transformation propoerties (equivariance properties, if you wish). If a and b are vectors in R³, then

$a\times b=\star (a\wedge b)$ (where $\star$ is the Hodge star)

is an element of R³, hence a vector. Your pseudovector claim says that the cross product operation is not equivariant under the antipodal map. But what the operation produces from two vectors is a vector for your average mathematician. What's happening here is not really different from multiplication in R: -a * -b = ab, not -ab, so multiplication is clearly not equivariant under x --> -x, but this in no reason as such to claim that product of two reals is not a real but a "pseudoreal".

In fact, if a "scalar" flips sign under under a parity inversion then it is a pseudoscalar, not a (true) scalar. This difference is also important in physics.

As said, things are different in the context where the definition of a vector is different, but that shows that the "pseudovector controversy" is not 100% clear cut even when all participants are right within their own reference frames.

I'm quite aware that this area suffered inconsistencies in the past (especially by Gibbs!). However, the indisputable point is this: if you define a vector as Gibbs did and calculate the cross-product of two vectors so defined, the resulting vector will flip sign when you do, for example, a parity transformation. This is not acceptable either in math (ambiguous) or in physics (the world collapses -- just kidding!), as I explained in cross product handedness discussion. To save Gibbs' vector calculus, the concepts of pseudovectors and (true) vectors were invented and everything works fine (the world does not collapse when you see yourself in the mirror) provided that the special rules explained in the cross product handedness discussion are assured for every equation you use. Further, note that with Gibbs vectors one needs a metric space too, and pesky coordinates are required.

BTW, I decided to use the pseudovector (instead of axial vector, or other) terminology because it seemed more extensively used in WP and is usually taught. I thought it was great not to have to talk about "dual vector space" and 1-forms -- that might make the whole subject harder for a beginner. And, in the way it was done, the cross product could be correctly defined, on first sight, as an ordinary (true) Gibbs vector.

Of course, everything works better with Clifford algebra! Happy will be the day when undergrads can learn physics directly using Clifford Algebra.

What a quick look at vector and related articles shows is also that there is some work to be done to have coherence in definitions involving vector spaces, inner product spaces and so on in a way where physics conventions do not abruptly change into mathematician's definitions or the other way round when an unsuspecting neophyte clicks a wikilink...Stca74 14:11, 22 May 2007 (UTC)

I also updated some articles in the direct dependence of cross product. Much more work surely needs to be done.Edgerck 17:55, 22 May 2007 (UTC)

Yes, what you write is quite clear. However, for the purpose of assessing the decay time of indisputable facts on Wikipedia, I still think the pseudovector topic is not perfectly suitable as there are multiple definitions for the concepts being discussed, and those are not always made explicit in the article under discussion. I think the following quotation from you above serves to illustrate: "if you define a vector as Gibbs did and calculate the cross-product of two vectors so defined, the resulting vector will flip sign when you do, for example, a parity transformation." [emphasis mine]. True, the Cross product article links to vector, where allusions are made to the Gibbs defition. However, no proper formal definition can be found by followin that link, and it is quite understandable if someone reading cross product fails to notice what the intended definition behind the discussion is.

What plays a role here is the seemingly subtle semantic difference of whether "scalar product of two vectors a and b" refers to the vector-valued function of two arguments or to the value of that function on a and b. It is about the former that one can say it is a pseudovector (it is only for the former that equivariance is meaningful). A source of confusion is that a physicist convention would be to call the former a vector / pseudovector while people with pure maths background tend to reserve the name "vector" for the latter and insist calling the former a (O(3) or SO(3) equivariant) vector valued function. Similar confusion arises easily with regard to tensor / tensor field as witnessed on the relevant Wikipedia talk pages. And as we know, this is linked to whether one prefers definitions in terms of coordinates and components or "intrinsically"...

What this particular example indicates to me is not so much that factual information decays on Wikipedia (while that itself is probably quite true as shown by other cases) but that unless we have full clarity, especially in articles where two or more closely related teminological conventions can potentially clash, we shall continue to see edits moving back and forth as groups of people interpret things acording to the context most familiar to them. In this specific example a lot can be achieved by incorporating sufficiently precise definitions (now missing in vector!) and being explicit on different usage for common terminology. Stca74 09:13, 23 May 2007 (UTC)

What you comment is indeed part of the context of the information decay that we want to measure. To simplify things, I chose topics to try to reduce the influence of what you describe, and also to reduce the influence of audience variations. The expected audience provides the default interpretive context, that we design for.

Regarding full clarity, Niels Bohr once said that the antonym to truth is clarity. A true statement cannot be clear, and a clear one cannot be true. So, with this warning in mind, I defined when to stop in my edits, to achieve a good compromise between these two warring goals.

This subject has to do with an area of my research on identification theory. When we identify something, uncertainty is unavoidable. To reduce uncertainty, it is useful to divide it first in two orthogonal components: accuracy and reliability. Accuracy has to do with conceptual coherence, while reliability has to do with perceptual coherence.

So, rather than look for the perfect topic for assessing the decay time of indisputable facts on Wikipedia, which would be impossible to identify, I tried to maximize both accuracy and reliability when choosing topics and their audience, as well as also when doing the edits.

What's the default interpretive context for the "cross product"? Well, it is mostly used in high school math, engineering and undergrad physics. It has a very limited context, and it was invented for it. In these areas the reader is already conditioned to the Gibbs model for vectors. So, that's the natural context I believe most readers would use to interpret the page. For those readers, vectors/pseudovectors is a simple, common terminology. Many electromagnetic theory text books use it, for example, and they need to make the distinction clear.

The choices for the physics articles followed similar principles.

Thanks for the comments. Edgerck 10:12, 23 May 2007 (UTC)

(edit conflict) I have to agree with the points made by Stca74. In this case, many things depend on what definitions of cross product or even vector are being used. In this sort of case, it is not helpful to speak of correct/incorrect information, saying things like "it is actually a pseudovector", even if the pseudovector definition is the most useful. It is much better to spell out the different ways of looking at it. Then you can explain the advantage of defining the cross product as a pseudovector in the context of transformations, without suggesting that the vector definition doesn't make sense just because it doesn't have properties that are not relevant in other contexts. JPD (talk) 10:26, 23 May 2007 (UTC)

(post edit conflict) I think the approach I suggest above is also the best way to deal with your assumptions about readers. Your assumptions seem faulty to me on many levels, but making the context clear is a good way to deal with any reader. JPD (talk) 10:26, 23 May 2007 (UTC)

Ruminating on the topic whilst gardening today, it occurred to me that wikipedia is very much like a garden. You may plant a flower (or a particular interpretation of a topic), but unless it is maintained other gardeners will plant their own flowers and weeds will tend to grow. So it becomes unsurprising that a particular interpretation declines and further that maintenance is vital for the garden to flourish. Indeed weeding is what a lot of long term editors spend much of their time doing. Wikipedia is a very different sort of beast to paper as it is in constant flux and so obeys a different logic. --Salix alba (talk) 13:45, 23 May 2007 (UTC)

I am a believer in intellectual tolerance. Different people actually see different versions of reality.

This was exemplified historically in the 1500s, by a native group in South America refusing to see and acknowledge the presence of Europeans when their ships appeared and they even set foot on a beach where the natives were -- the natives happened to have a firm belief that nothing existed beyond the horizon, so no one could possibly come from there.

This can be explained by understanding the nature of trust. My perception of reality is colored by what I trust. Albert Einstein preferred to fudge his own cosmological equation for years (adding an ad hoc cosmological constant) in order to forecast a stable universe according to his philosophical beliefs, rather than accepting the result of singularities and a big-bang solution as predicted by his original equation (see Wheeler et. al., Gravitation, ISBN-13: 978-0716703440). But, finally, when confronted with astronomic data measured by Hubble (the Hubble), he conceded. Still, even though black-holes are predicted and described by Einstein's equations as well, he wrote a paper proving that black-holes did not exist (using what we know today to be a contrived example). That was never retracted, even though the authors of the black-hole theory were literally next door.

Of course, my measurement method can and should be contested. I believe it will just prove itself, as this is the result of many years of experimentation in this field, using has shown itself to be a solid model. While there is always a possibility for some erudit edit that correctly erases what I defined as correct information, this can be easily weeded out from the measured data.

In the particular case of the cross product (and other math articles that I edited in this experiment), I think that most mathematicians would rather not use it -- and so, most probably, the default audience will be what I assumed. If mathematicians (perhaps motivated by this experiment itself!), decide to edit it, still the mathematical physics established terminology of vectors/pseudovectors used to describe what is actually a second order tensor should be kept, so the correct information tag should not disappear.

Concerning the garden comment, I agree with Salix alba's insight. And this is, fundamentally, a limit on the trustworthiness of WP information.

My initial motivation for this experiment was to measure what Salix says and which I understand in terms of order decay -- the garden order decays -- as an entropy increase (a natural process).

It is a limitation not only in efficiency (doing the same task over and over again) but also because, after all, it matters not that some POV says that the cross product of two (Gibbs) vectors is a (Gibbs) vector (many textbooks say so!) and this is verifiably quoted in WP according to all the WP rules for article content. Lo and behold, upon a parity transformation, the answer is wrong. It matters not that some POV says that the photon has a "relativistic mass" and this POV is, likewise verifiably quoted in WP according to all the WP rules for article content. This notion just reveals itself to be inconsistent with reality (the Hubble shock), and in disuse.

How can we preserve (POV) diversity, tolerance, and yet prevent the decay of trustworthy information in WP? I don't have the answer but I am presenting the question -- with a method to help measure its importance.

Of course, people may say that this whole approach is over-simplified. But to make some progress in this, I believe we need to cut to the core issue first. As a further benefit, we shall not run out of work in improving it. Thanks. Edgerck 19:00, 23 May 2007 (UTC)

Essentially, I find your thesis biased and flawed. It is biased because it identifies certain information as trustworthy, on the basis of your own POV. Wikipedia strives for a neutral point of view, which perforce includes perspectives other than your own on what is accurate and what is not accurate. (It should suffice to demonstrate this by pointing out that you limit your definition of "trustworthy" to "articles in physics, mathematical physics, trust theory, and other subjects in my core professional areas" and then define said information as the version that a "subject matter expert would most likely select". In other words, the version is your version, and the expert is you!) It is flawed for two reasons: first, because "trustworthiness" as you are using it is a disguise for "truth" rather than fact, and Wikipedia makes a point of asserting that it does not intend to promote truth. Even Wikipedia's policy of attribution is no guarantee of truth, nor fact; the closest Wikipedia has to that is consensus, which is the process by which material additions and deletions are vetted; watchlists of concerned users, and the process of discussion to arrive at consensus, are the best and only safeguard against your so-called "decay". The second reason it is flawed is that "trustworthy" information may be deemed to be irrelevant, superfluous, or redundant, even if it is trustworthy by some (as-yet-unestablished) objective standard. As you should expect your content--even content you deem trustworthy--to be mercilessly edited at will, if you find that such content is not surviving for reasons other than thoughtless vandalism, you may be more comfortable on forked projects, such as Citizendium. Robert K S 19:22, 23 May 2007 (UTC)

The idea that the observer does not influence what is observed was shown to be incorrect in physics by Heisenberg with the uncertainty principle. Today, this is well accepted outside of physics. The act of measurement itself introduces an irreducible uncertainty in the measurement.

Of course, this also helped question the so-called scientific impartiality view. How to remain impartial, when impartiality is impossible? One solution is the method that I followed: all my assumptions and methods are laid bare for examination, critique, and can be changed to provide a different view if so dictated by the experiment itself (i.e., changed to try to minimize influence).

For example, I took pains in describing what this experiment considers to be correct information both in terms of what it is as well as what it is not.

Yes, this is my version of what I consider (as a subject matter expert with verifiable qualifications) to be what a "subject matter expert would most likely select".

But I also present to the reader exactly what that version would be (even during the experiment, to preserve a trail of cause-effect), as you can see above in the list of what I consider established facts.

So, I do present the context of the experiment and what the metrics are.

Finally, in terms of possible dynamic changes in the overall metric used (for example, one of my correct information points is shown to be not as clear as I would desire), it is a simple matter to weed out that point (justifiably) from the measured date set.

The metric may be contested and changed even post-experiment, at any time. This is a dynamic experiment in a dynamic environment, with a metric notion that is also dynamic. Thanks. Edgerck 20:02, 23 May 2007 (UTC)

This is certainly an interesting experiment. To some extent what you are doing is like throwing rocks into a pond: You are disturbing the system and seeing how it reacts. The problem with this experiment is that many of the articles that you are touching are somewhat refined such that an edit which is not in accord with the "dynamic" of the article will be resisted even if it is correct. An example is your special relativity edit in which you brought in a very specific example which myself and another felt was not in accord with the article itself due to the subtleness of the concepts being presented. (The accuracy was not in doubt).

First of all, thank you for your comments, and I understand these might be sensitive topics for you right now; so I am happy we can promote this dialogue. My interest with the edits was not to catch anyone in a public trap. That's also why the experiment is laid bare to all while the experiment is in session.

The first problem you mention is described in the article (top item in this page). That is actually one of the reasons why special relativity was chosen, as explained there. On the Internet, it is also common for people to speak through proxy identities or act in cabals, to create a false "consensus". There is a lot of this in special relativity pages; I have seen heated WP editor exchanges were an editor was citing a crank author without realizing it. In WP for special relativity, some editors claim "I am an expert, this is high-schooll stuff" and "we are all experts" while the dialogue actually reveals in some cases a serious wanting in basic physics knowledge, and in more cases a lack of scholarly behavior (for example, to concede after making an error, rather than jumping to another topic as a way of diversion).

I will refrain at this time (while the experiment is in session) from saying my POV on your decision not to revert your edit; I can just objectively point to contradictions between what you wrote above and the article history, and talk page. Please also note that at each "end" of this experiment, at various times, all data will come from WP itself, objectively and publicly available, for history, versions and talk pages. All data is publicly verifiable.

BTW, there was another, extensive, seeded edit that I did in Introduction_to_special_relativity#Common_misconceptions that was reverted by you with no comments and no response so far for my request for justification both in the talk page and your talk page. You may want to take a look into that.

My experience has been that thoughtful edits done in accord with the spirit of the article and with respect for the other editors do get retained. It is when someone comes in and tries to steamroll the other editors that trouble results. I myself have sucessfully done article rewrites (as was the case with general relativity over a year ago), and even some "major reverts" (which is when a regularly editted article is returned to the state it was in more than a month ago). So how you edit is at least and important as what you edit. It is easy to create text that gets reverted and/or corrupted, but that does not mean that this will happen to all articles. --EMS | Talk 21:42, 23 May 2007 (UTC)

Some page groups are more open to ideas than others, I think this is natural. What I am trying to measure is something different and, because I did a fairly large number of edits, there should be a "smoothing effect" of rejection spikes or just "bad moments" in the final results. It is possible that some good but radical changes are rejected. But that's also what I want to measure, as the 'acceptance of change in WP', not just the 'trustworthiness of information'. After all, if errors cannot be changed (because editors are too strongly bound to articles) then this is also a factor that reduces the trustworthiness of information. Thanks again. Edgerck 23:04, 23 May 2007 (UTC)

You are going to run up against all hinds of effects here. In general, articles tend to get better over time, but studies have shown that the best ones are the ones that are the most actively editted. The 2004 Indian Ocean earthquake article ended up being an authoratative source of current information as more and more information on that catastrophe emerged. Special relativity is a different type of beast, caught between a number of concerns that have pushed and pulled it in several different directions and without having had an editor come along who is ready, willing, and able to clean up the mess. However, there are certain parameters that have been implicitly agreed to even so, and one is to treat there as being a universal potential to convert mass into energy and vice versa. At the least, you will need to justify your POV on that one. (We should discuss that bullet point sometime soon BTW - I do not agree with your POV but I am not sure the current text is ideal either. I am not going to respect an outright demand to "change my ways" but I am happy hash things out with a fellow editor who is knowledgable and is willing to listen.) Examples of articles that have been cleaned up single-handedly are gravitation and general relativity. Obviously those articles are not static, but the reorganized structure has not been changed much since the rewrites went "live" in each case. (Rewrites are often done off to the side and the other editors are usually allowed to review and enhance the rewrite before it replaces the pre-existing version. That is one way in which the opnness of Wikipedia is an asset.)

Hopefully this will give you a slightly better sense of how things get done here in Wikipedia. --EMS | Talk 03:01, 24 May 2007 (UTC)

Thanks, that's a good summary. Yes, I did see your good work (still incomplete) in the giant article for GR. Comments by order:

• On the subject of lack of complete equivalence between mass and energy, my justification is the given reference.
• On the bullet point issue, I would prefer not to cite any example, and just keep the short phrase I had before the example. I think the matter is self-evident and already linked. I added the example just for reading coherence in the page, as the other bullets have examples.
• On the Common Misconceptions issue (not cited by you above but reversed by you without comment or reply to my requests for justification), references were given for each point made.

Edgerck 04:02, 24 May 2007 (UTC)

I think that we may be dealing more with orientation and semantics than any outright disaggreement on the physics involved. The one point I got from the references that seems to accord with what you are trying to say is that the photon is massless but has energy. So energy and mass are not equivalent, but they are interchangable. (A photon absorbed by an object will cause the mass of the object to increase, for example.) As for the other bullet point, they are elaborated on, but not necessarily with a specific example. On the issue of mass-loss vs. binding energy in nuclear reactions: I see those views as being two statements of the same thing. The change in rest mass is due to the release of binding energy and vice versa IMO.

Beyond that, I would want more evidence that the change of paradigm thet you are calling for is reflected in the litereature as a whole. As you have seen in other cases, it is easy to justify an improper POV by using inappropriate sources, or even by being overly selective with reliable sources. With relativity, there is not lack of sources after all. --EMS | Talk 15:43, 24 May 2007 (UTC)

The reference I provided specifically supports the statement of lack of complete equivalence between mass and energy. I also took care to provide the page numbers, so that the reader does not have to waddle through the entire book. It is also a mainstream author and book. And it's not just an opinion, it is supported by sound examples. So, I just have to ask you to please read the referenced page numbers given. There, you will find that the statement you call "paradigm shift" is provided verbatim, and explained. To make your task easier, the given reference can be read (including all cited page numbers) without cost at books.google.com.

As I have seen in other cases in special relativity, it is easy to justify keeping an improper POV by demanding to see many sources of authoritative information that show otherwise, when a simple google search can show that the improper POV is not mainstream in physics.

As I have also seen in other cases in special relativity, (see footnote [3] in [seed version of photon], where "seed version" refers to the WP version current when phase 4 of this experiment was closed), it is easy to justify an improper POV by demanding that something that is published 3x and more be considered within the WP reliable sources policy. However, not every published source is equally updated or authoritative on the subject matter. In the case of footnote [3], it was claimed in WP (as a result of this flawed use of WP reliable sources) that the photon has a "relativistic mass". This is 3x incorrect, according to updated and authoritative verifiable sources, because 1) the photon is massless (as you also agree above); 2) the notion of "relativistic mass" is no longer used by physicists (as referenced in [seed version of relativistic mass]); and 3) the photon has an undefined "relativistic mass" (because M=γm cannot be calculated, op. cit.).

I do not want to be overbearing and I feel I already discussed all clarifications on my edit and references. So, for right now, I just want to leave the matter in your hands and in the hands of the community. I'll be very happy to just watch and see how the system processes the correct information (see my definition of it in main section) that I inserted, referenced according to the WP reliable sources policy, and clarified when contested. Thank you for your kind review. Edgerck 18:57, 24 May 2007 (UTC)

As long as you are not trying to outright impose a POV here, I am happy to work with you on this. Editing a more mature article is not a trivial thing. How about if you get back onto talk:special relativity and list the sentences which are giving you heartburn? I for one do agree that photons do not have an mass, relativistic or otherwise. I don't see what I edited the bullet point to as saying that they do have relativstic mass, but then again is does not say that they do not have it either. Even so, do note that this is a minor point and it won't be placed into the bullet point just to have it be there. It has to "fit in" instead of being a secondary issue better covered either later in the article, in another article, or possible even in a textbook. --EMS | Talk 20:53, 24 May 2007 (UTC)

Thanks. All I had to say and reference is already in the archives of talk:special relativity and other pages, in rather lengthy comments. As you correctly infer, I'd surely have more points to ponder in regard to the present accuracy of special relativity and some POVs expressed in the talk lists, but I prefer not to be overbearing with too many points. I also want to give time for the community itself to process the information and do the necessary edits, rather than just driving edits directly. Consensus takes time to build. We must all be patient. I also like that "disengage" is part of the WP process, and I am applying it. Edgerck 22:39, 24 May 2007 (UTC)

Then do as you think is best. The SR page is in need of some to take "ownership" of it and push it in a different direction, and given your interest in the topic you may be the person to do it. Even so, disengaging and taking your time to study it and Wikipedia is essential to being able to produce a useable rewrite. (One thing is that you will need to deal with the whole topic in a rewrite and not just your pet peeve of the treatment of E=mc².) You are correct that my main focus, when I have time to do more than watch for vandals and kibitz, is to work on the general relativity article. Given that most of my spare time goes to my original research, I cannot do more at this time. --EMS | Talk 02:38, 25 May 2007 (UTC)

Thanks again for your kind remarks. This work is in public domain and I feel no attachment as to "ownership". Following WP:OWN might be the first early recommendation of this experiment, to reduce this binding, all-excluding force between editor and article. Physics is fun and editors should have fun in discussing it too.

As a pending matter, I am still waiting for you to kindly recall or justify your revert of my edits in Common misconceptions (see above). Edgerck 05:45, 25 May 2007 (UTC)

Asymmetry of mass-energy equivalence

I'm still stuck in my understanding of your statements 4 and 5, above. Can you provide some other supporting resources, or some better and more complete explanation? Thanks, Ed. Robert K S 22:50, 26 May 2007 (UTC)

Robert, please note that the item numbers were re-assigned today, with some items being subdivided. I think you mean the short mass and energy points. I have two suggestions:

1. read all the items first, as there is supporting information in latter items (ie, it is not possible to keep information as compartmentalized as I would wish); and
2. do a google search, try also books.google.com, as it is easy to find numerous authoritative sources taking the correct information, or mainstream, position reported in the items.

Hope this is helpful. Edgerck 23:53, 26 May 2007 (UTC)

It's not. I have been trying to satisfy this for myself for some days. Google searches on asymmetry mass-energy equivalence return nothing relevant. Even searching for Not every energy corresponds to mass returns as its first result a page that reads, "According to Einstein, to every energy there corresponds a mass". (The second result is your user page on Wikipedia.) Perhaps you can suggest some better Google search terms or some other pages or forums where I might ask about this. Sorry to be a bother, but I really want to get up to speed so that I can be on the same page with you, because I sense your dedication to improving these pages, and I feel like my ignorance is holding me up from being a collaborative contributor. Robert K S 02:15, 27 May 2007 (UTC)

Robert: If "to every energy there corresponds a mass" then a photon would have mass, but it does not. So, if an isolated (free) atom spontaneously emits a photon then that atom's mass is reduced correspondingly and no other mass is created to compensate -- even if you consider the system to be so large that the photon is still inside it and the system is closed (isolated).

Next, please read all the paragraphs after the first paragraph after eq. 15 in Okun's paper in Phys. Today., until the end of that section. The paper is at http://www.physicstoday.org/vol-42/iss-6/vol42no6p31_36.pdf

After that, because books are harder to be crank vehicles than websites, go to books.google.com and search for "massless photon". Once you get better technical search terms, from the books, it should be relatively easy to find current mainstream references that the photon has no mass. So, if an isolated atom emits a photon...what happens with the system's mass?

Hope this is more useful. Edgerck 03:00, 27 May 2007 (UTC)

Can a free atom really emit a photon and have its mass reduced? I thought a photon being emitted would be concomitant with one of the atom's electrons leaping from a more energetic to a less energetic orbital. Thus the atom's energy is reduced and its mass in unchanged. Is my understanding incomplete? Can atoms emit photons independent of what their electrons are doing, and thereby change their masses? Which subatomic particle(s) account for the lost mass? Robert K S 07:58, 27 May 2007 (UTC)

You wrote: "Thus the atom's energy is reduced and its mass in unchanged." Do you find a problem with your phrase when you calculate m=Eo/c² in the atom's rest frame, and compare the result for m before and after the photon is emitted? Thanks.Edgerck 17:40, 27 May 2007 (UTC)

Nope, I don't see a problem, which is why I asked you in the first place. Please answer my questions. Which subatomic particle(s) account for the lost mass? Robert K S 19:54, 27 May 2007 (UTC)

Robert, it was already below, when you left the msg above -- check the timestamp. Edgerck 00:03, 28 May 2007 (UTC)

BTW, the increase/decrease of mass with energy originates not in the object but in the geometric properties of space-time itself. See in Edwin Floriman Taylor, John Archibald Wheeler, Spacetime Physics: introduction to special relativity, op.cit in reference page.Edgerck 17:40, 27 May 2007 (UTC)

Would you agree that the subatomic particles that constitute an atom have known and fixed rest masses? Robert K S 00:07, 28 May 2007 (UTC)

Definiton of rest mass for systems of objects

I have carefully read your new user page, and I stopped dead here: "Contrary to classical physics, an isolated (free) system can reduce or increase its mass by internal mass energy conversion. For example, mass is not conserved when an isolated body (in a system considered large enough to be closed) emits a photon..."

I think I have finally found the problem why there is so much disagreement here. How do you define the mass of a system of objects? Well I would define the mass to be the total energy of the system as measured in the center of momentum frame of the system (divided by c^2 if you like). Some systems, like free photons, have no such frame and therefore no mass. So far, so good.

Under this definition: If a photon is emitted by an atom what happens to the mass of the system atom+photon? We both agree that the momentum is conserved and the energy is conserved. Using my definition for mass the mass must obviously be conserved too. So if you say the mass is not conserved you must somehow use another definition of mass. It seems to me that you just add the masses of the constituent parts of the system, but then how do you define what a part is?

So, what is the mass of a system of objects?

(please sign next time). Please read my reply above. It shows that the atom looses mass in the rest frame, as it must because it has less energy. Remember that the photon's energy does not count as mass (as you know). Regarding your last question, please see the answer list at http://en.wikipedia.org/wiki/User:Edgerck#Mass_and_energy_in_special_relativity -- there are a couple answers that apply. Thanks. Edgerck 03:05, 27 May 2007 (UTC)

At least we have found the problem. You really count only the atom. You can see from my definition (I made it bold in the above paragraph) that I *do* include the photon. I think it is better to leave the discussion at this point. I see that we do not only talk about different definitions of mass as in relativistic mass and rest mass, but that we also have two different definitions of rest mass, and this has caused all the confusion. Thank you for the astoundingly fast replies and sorry for the missing signature (I don't want to be known as "ghwqo34nvg" ^^).

There is no photon rest frame for a photon+atom system. Rest mass is the mass of the body at rest, for which the photon has none. Thanks. Edgerck 14:49, 27 May 2007 (UTC)

I just wrote a lengthy answer, but on a second thought, I prefer to stop discussing and do something useful.

Asymmetry of mass-energy equivalence

(continued from same thread in Archive 1)

BTW, the increase/decrease of mass with energy originates not in the object but in the geometric properties of space-time itself. See in Edwin Floriman Taylor, John Archibald Wheeler, Spacetime Physics: introduction to special relativity, op.cit in reference page.Edgerck 17:40, 27 May 2007 (UTC)

Would you agree that the subatomic particles that constitute an atom have known and fixed rest masses? Robert K S 00:07, 28 May 2007 (UTC)

Yes, but their masses are not present with those values in the atom. When those subparts united to form the atom, their mass was reduced from their rest mass values by the binding energy. So, the atom has a rest mass that is less than the sum of the mass of its constituents. See specific item on binding energy in the main list of answers, with references. Edgerck 00:27, 28 May 2007 (UTC)

Robert: There is one more information for you on "mass". I am copying from the reference below. A goal of modern quantum field theory is to eliminate mass as a primary property of matter, so we are pursuing a mainstream objective of contemporary physics. For example, it is believed that the sum of the masses of the 3 quarks constituting protons or neutrons is only 2 or 3 percent of the inertial mass of those protons or neutrons. Most of the mass is attributed to the energy associated with quark motions and gluon fields, but precisely how this energy translates into the property of mass through a Higgs field is not easy to understand (see two recent articles by F. Wilczek in Physics Today, Nov. 1999 and Jan. 2000 for an overview). In http://www.calphysics.org/questions.html Hope this is useful. As you go more and more to subparticles, all that is left is energy. That is what we expect today. It would be a surprise to find mass as a primary property of matter. Edgerck 00:57, 28 May 2007 (UTC)

So what is the scale at which rest mass has a valid definition and does not need to be conflated with energy, as your model of the atom does? Robert K S 01:17, 28 May 2007 (UTC)

Robert: Please explain what you mean by "my model". BTW, the research paper cited above is speculative -- note that it says "it is believed", and "goal" for example. It is expected, but there are other alternatives as well. Edgerck 01:31, 28 May 2007 (UTC)

BTW, "rest mass" is defined with two conditions. Please see main answer list. Isolation is certainly not satisfied when the particle is bounded in the atom. Edgerck 01:33, 28 May 2007 (UTC)

By "your model" I mean the one you describe, where a massless particle may be jettisoned and mass may be lost. This model conflates the definitions of mass and energy (into "mass-energy") and neglects conservation of mass for conservation of "mass-energy". It seems like you're using the word mass to mean "mass-energy" without wanting to say as much. Or, perhaps I am completely confused, and you can help clear it up. Robert K S 01:38, 28 May 2007 (UTC)

Robert: Definitions of mass and energy are not conflated (mixed). In SR, mass and energy are apples and oranges:

• Mass is a scalar, an invariant and is not conserved in isolated (free) systems;
• Energy is the time component of the energy momentum 4-vector (ie, not a scalar), is not an invariant, and is conserved in isolated (free) systems.

As noted, the comment about mass, if you mean invarient mass, is wrong. Invariant mass of systems is conserved in isolated systems. SBHarris 04:36, 29 May 2007 (UTC)

Sbharris: I refer you to the standard, authoritative, current textbooks that I cited according to WP:NPOV and WP:RS, for any such notions as discussed here. I fully agree with those sources and don't think these issues are the least controversial today.Edgerck 18:18, 29 May 2007 (UTC)

What could be more different? All the properties above are different for each one. In addition, there is massless energy but there is no energyless mass.

Comment. True, but you'll find that "massless energy" is simply energy which has been made to appear by shifting reference frames to those which don't minimize energy. In the one inertial frame which minimizes system energy (and there always is one, for any system with at least one massive particle-- the COM frame), all system energy apears as mass/c^2, and there is no such thing as massless energy. The only system for which this is not true is one containing one or more photons traveling in exactly the same direction, and nothing else (no massive particles). For such a system, there is no mass and no COM frame. However, energy for such a system is also completely arbitrary (it's totally frame dependent and can be whatever you like, from next to zero to next to infinite, so in that sense, is not conserved, either. Nor is momentum. The conservation of both energy and momentum depend on the presense of non-zero invarient mass in the system (which is not the case for one photon, or more than one if going in the same direction). If no mass (invarient mass) is present, nothing (not mass, momentum, or energy) is conserved. SBHarris 04:36, 29 May 2007 (UTC)

BTW, Invariance and conservation are not the same. It is clearer to reserve the term "change" when discussing conservation, and use the term "difference" when discussing invariance. If a quantity is invariant, then it will have the same measured value in any inertial reference frame. For example, momentum of an isolated (free) system is not an invariant quantity, since two observers in relative motion, each applying the same operational definition of momentum, may obtain different values for the momentum of the system. If a quantity is conserved, then its value, as measured in a particular inertial reference frame, does not change over time. As ref.'d in the answer page.

Hope this is useful. Edgerck 01:48, 28 May 2007 (UTC)

Comments on relativity postulates

You were doing fine until you got to this:

• Mass can be converted to massless energy according to E=mc². Every mass corresponds to energy.

COMMENT: Well, in short, no on the first part about mass being converted to massless energy. That never happens. The basic reason being that if "mass" (meaning invariant mass) is ever present, that mass always must remain as mass. One consequence is that a massive particle cannot be converted to a single photon, or 2 photons traveling in the same direction-- the sort of system where mass and energy are undetermined and discussed above. Yes, if mass is present, a sort of "viewpoint" energy can be added to a system without mass, by shifting frames to one in which energy is not minimal. But that's just taking a resting baseball and giving it "kinetic energy" by flying by it. It's added energy from relative motion, and doesn't count as invariant mass in the first place, so it doesn't involve conversion of any mass to massless energy. Invariant mass itself never changes in closed systems. Invarient mass stays as invarient mass even when converted to photons, because those photons will be traveling in opposite directions such that an invarient mass will always be present. And it will be the original invariant mass, so long as the system remains closed. SBHarris 04:36, 29 May 2007 (UTC)

• Energy can be converted to mass according to m=E/c². Not every energy corresponds to mass.

The only energy that doesn't correspond to mass, is the energy due to frame-shifing. Invarient mass, which is frame invarient, can never be turned into massless energy. It's mass remains and (in closed systems where it's not physically removed) is always conserved as mass.SBHarris 04:36, 29 May 2007 (UTC)

• Contrary to classical physics, an isolated (free) system can reduce or increase its mass by internal mass energy conversion. For example, mass is not conserved when an isolated body (in a system considered large enough to be closed) emits a photon, or undergoes nuclear fission or fusion. However, an isolated (free) system cannot reduce or increase its energy by internal mass energy conversion. ,

The first sentence is complete baloney, and I'm curious if Landau and Lifschitz ever actually said it. Supply quote, please. If they did, they screwed up badly.SBHarris 04:36, 29 May 2007 (UTC)

• Two different isolated systems, with the same energy content, can have different invariant masses. For example, a system of two photons can be massless or have an invariant mass up to 2E/c², where E is each photon's energy (assumed equal), as a function of relative momentum orientation for the photons. So, in such a system, independently of the energy content being held constant at 2E, the invariant mass may vary from zero to 2E/c².

So what? To hold energy "constant" at 2E, you must shift frames a very great deal, going from velocity zero to c, on the axis between the two photons, in order to make them go from 1) traveling in opposite directions where their mass is indeed 2E/c^2 and your transverse velocity to the line separating them is zero, to 2) a system in which the photons are now traveling in the same direction, and where the system is massless but you are (wink, wink) going at speed c in order to make two photons that once had a radial component to their velocity, now *fail* to have one. In practicality, you can't quite do it.

In any case, if you must demo two "different isolated" systems with the same energy content but different invariant masses, you can choose a system with one baseball going really fast at 0.866 c or so, vs. another with two baseballs not moving at all. We've jiggered they systems to have the same energy content by screwing with the inertial frames, but again, so what? I don't know what this is supposed to illustate except that you can't trust all energy to show up as invariant mass. But we never said you could.SBHarris 04:36, 29 May 2007 (UTC)

• The term "rest energy" is used for the energy content Eo of a body that is 1) isolated (free), and 2) at rest relative to the observer. Due to the special relativity theory mass-energy equivalence, the rest energy corresponds to the mass m = Eo/c² (this equation cannot be applied to a photon). In general (including photons), the invariant mass is given by the energy-momentum relation (mc²)² = E² - (pc)². If conditions (1) and (2) apply, then the invariant mass is equal to the rest mass. If the isolated (free) condition no longer applies (e.g., the body is placed near another body) for a body originally with rest mass m, its invariant mass will be less than m.

This one needs to be translated from the Russian. "Placed near?" Free bodies can be attracted to each other and the invariant mass of the system doesn't change as it happens. All that happens is that potential energy is traded for kinetic energy. However, invariant mass does not change in these processes, so long as the system remains closed.SBHarris 04:36, 29 May 2007 (UTC)

• In classical mechanics, energy is always expressed relative to a reference, arbitrary energy level, and can be positive or negative; only difference in energy is a measurable quantity. The "rest energy" (see item directly above), however, is defined absolutely and is always positive.

True.SBHarris 04:36, 29 May 2007 (UTC)

• When physics laws are written as equations, it should be possible to make an arbitrary choice of the coordinate system (including handedness and units). To avoid problems, one should be careful when comparing quantities to verify that they behave equally under all transformations that need to be considered; for example a scalar cannot be compared to a vector component. The different invariance properties between mass and energy are due to the fact that energy is a component of the energy momentum 4-vector (E,px,py,pz), while mass (a scalar) is its magnitude. In special relativity, it is common to use units with c=1, where c is the speed of light. When using c=1 units, it is a common mistake, for example, to write the mass energy equation as m=E and infer that mass and energy are one and the same thing, or write the energy-momentum relation m² = E² - p² and infer that, in a closed system, mass must be conserved because the energy momentum 4-vector is conserved.

Mass and energy are not the same thing. However, it is not a mistake to infer that because the energy-momentum vector is conserved, mass must be conserved. If mass is defined as the length of this vector (invariant mass), it's obviously conserved. This is very simple. Only when certain physicists perversely insist on defining mass as other than invariant mass, does it fail to be conserved in closed systems.SBHarris 04:36, 29 May 2007 (UTC)

• The mass-energy equivalence Eo =mc² changes the classical physics mass and energy conservation laws for isolated (free) systems: 1) contradicts conservation of mass (mass can be converted to massless energy); and 2) allows conservation of energy to be calculated in absolute terms (as rest energy).

Eo =mc² remains correct if m is invariant mass and E is rest energy or minimal system energy (total energy when p is zero).SBHarris 04:36, 29 May 2007 (UTC)

• It is a common misconception to consider that mass is completely equivalent to energy in special relativity. In spite of views endorsed by well-known physicists in the past (1905-1980) and popular philosophical discussions otherwise, mass and energy are not two forms of the same thing:
  * Mass is a scalar, an invariant and is not conserved in isolated (free) systems; while
  * Energy is the time component of the energy momentum 4-vector, is not an invariant, and is conserved in isolated (free) systems.
  Energy also appears as a more fundamental quantity; while there is "massless energy" (e.g., a photon), there is no "energyless mass". Conversely, while an energy does indeed correspond to any mass, the opposite is not true as mass does not correspond to every energy (e.g., a photon).

As noted above, this is not true if mass is defined as the norm of the EM 4-vector or the 4-momentum (units c =1). In this case, mass is most fundamental quantity, since it is conserved and invariant. Energy is only conserved, and then only when viewed in a single frame. Massless energy only appears as extra energy due to frame-shifting. Invariant mass can never be converted to massless energy, but retains its mass in all closed systems, in all transformations. SBHarris 04:36, 29 May 2007 (UTC)

• The principle that the mass of a system of particles is equal to the sum of their masses, even though true in classical physics, is false in special relativity. The mass-energy equivalence formula implies that bound systems have a mass less than the sum of their parts. The difference, called the mass defect, is a measure of the binding energy — the strength of the bond holding together the parts (in other words, the energy needed to break them apart). The greater the mass defect, the larger the binding energy. The binding energy is released when the parts combine to form the bound system. In particular, the total mass of two protons and two neutrons after they are brought together to create a helium nucleus is less than the total mass before, of each isolated (free) nucleon. The mass difference being the energy that is released when the four nucleons are brought together, divided by the speed of light squared. The mass difference and the energy released are related by the mass-energy equivalence formula: (mass before - mass after)c² = energy released; the energy released is equal to the difference in rest energies.

All true enough, but it should be noted that the mass defect only arises because (and if) mass has been removed from the system (ie, system not closed). The removed energy continues to have mass, as it is mass/energy of the invariant type, which cannot be destroyed or "converted" to anything other than mass. This is because the "mass defect" is calculated from the difference of two systems "at rest" or at minimal energy (zero momentum). Thus, all apparent mass defects are due to non-closure of sytems, and all mass defects represent removed mass which continues to have invariant mass. If this mass appears as heat or light, the heat and light continue to have exactly the missing invariant mass. Changing frames cannot change this, so long as all parts of the system continue to be viewed from a single frame. A 20 kT atomic bomb may release a gram of heat and EM radiation, but this heat and light still have one gram of mass, and they deposit this gram of mass on any matter which is heated by them. The mass defect appears only in cooled products, and this is true as much in nuclear physics as it is in chemistry. If systems remain closed and products are not allowed to cool, mass will continue to be invariant and unchanged.SBHarris 04:36, 29 May 2007 (UTC)

• A common misconception is that the main reason for the power of nuclear fission and nuclear fusion used in energy generation and atomic weapons is the mass-energy conversion given by Eo = mc². Historically, Eo = mc² has been connected with nuclear energy. In reality, the main energy contribution both in nuclear fission and nuclear fusion is due to binding energy conversion (see item directly above) to other forms of energy, not mass conversion (energy from mass conversion is small in comparison). The reason is that systematic trends in nuclear binding energies allow energy to be obtained by nuclear fission of heavy nuclei (heavier than iron or nickel) or nuclear fusion of light nuclei (lighter than iron or nickel). In nuclear fission, most of the energy released comes from the difference in binding energy when a heavier nucleus is split into lighter nuclei (that are much more strongly bound). In nuclear fusion, fusing lighter atomic nuclei to give heavier nuclei sets off energy because the binding energy of the end product is larger than the sum of binding energies of the initial nuclei.

I fail to see what the "misconception" is, as you've simply stated the same thing twice. The mass-energy conversion represents the binding energy, but this energy continues to have mass. However, it is now present as radiation and heat (kinetic energy) so that it is more destructive and not so neatly packaged. However, total mass remains constant in the process, so long as the system remains closed. SBHarris 04:36, 29 May 2007 (UTC)

Thanks for the comments. I'll use them carefully to verify if improving the style may be helpful for understanding the text better. The content is correct. Please refer to the given references for the original texts. Edgerck 06:01, 29 May 2007 (UTC)

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