Talk:Gravity/Archive 5

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Archive 1

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Archive 3

Gravitation is not gravity

I assure all that there is a serious difference between gravitation and gravity.

gravity is a force.
gravitation is just the tendency of object to move towards each other.

In Newtonian mechanics gravity is used to explain gravitation.
In general relativity, there is no force of gravity. Instead gravitation occurs due to the effects of spacetime curvature.

Becuase of this, I am rewriting some GR-related pages to describe GR as a theory in which there is gravitation without gravity. That is the correct semantics for it. I therefore cannot have both links pointing to the same article.

This page needs to be expanded. It, and not the gravity page, should have the parts now in the gravity page on GR and the new alternative theories. The gravity page should be devoted exclusively to Newton's theory, with GR, quantum gravity, and the like being mentioned (and only mentioned) in a "Status" section.

It is time to distinguish between these two related yet different concepts. It is time to straighten out the gravity page by taking advantage of it. Maybe amongst lay people these two words are synonyms, but it is not that way amongst physicists today. There is a difference, and it needs to be respected.

I trust that I have made my case. --EMS | Talk 04:44, 5 August 2005 (UTC)

I'm pleased that you use my definition of "gravitation" that I placed in Wikipedia some time ago to clarify some misunderstandings about gravitation, but I think that your effort to name "gravity" a "force" is a little bit misguided: "Force" is an ambiguous idea since there are "fundamental forces" (electromagnetic, strong, weak) and "pseudoforces" (gravitational, a.k.a. inertial). "Gravitational forces" (pseudoforces) exist in both Newtonian and Einsteinian theories, so do you call pseudoforces "gravity"? Or you call "gravity" a non existent Newtonian attractive gravitational force that about a century ago was thought to be a fundamental force of nature? But then why to give it a name if physically it does not exist at all? So I think that you propose to rename "preudoforces" as "gravity". Am I right? But they already have name: "inertial forces". So isn't it better to stick to the traditional terminology and just use "gravity" as anyone pleases? Jim 12:55, 4 September 2005 (UTC)

In the semantics of GR, pseudoforces create "gravitational fields". Gravity should be used exclusively to describes the Newtonian force of gravity. Realize that when you assume that spacetime is flat, you need to have gravity as a fundamental force to describe and explain how massive objects attact each other.

As for naming something that "does not exist": You need to step back and consider what it is that is being named. The name is attached not to the force, but to the concept of the force. Without the name, the concept cannot be discussed. That gravity does not really exist (according to modern scientific opinion) is irrelevant to the existance of the concept. By the way, without the concept of gravity, we never would have been able to come up with the concepts of general relativity eventually. --EMS | Talk 01:27, 6 September 2005 (UTC)

OK. You've convinced me. I'm starting using this distinction. Up till now I've been using "gravitational force" for "gravity", but I like better "gravity" since it's simpler. I just wonder how many people will understand correctly my texts. So I'll try to explain how "gravity" occurs in Einstein's theory without any "force". Please give me some critique of my article when you see it at "gravitation" page. Jim 15:02, 14 November 2005 (UTC)

You don't seem to understand this. In GR, one talks of "gravitation", not "gravity". Gravity without force is not gravity, after all. --EMS | Talk 17:15, 14 November 2005 (UTC)

So I'll place this proposed article here (see below) and then tell me what I don't understand in Einstein's theory. Jim

I thought that gravity was gravitation on earth. In other words, gravity is a special case of gravitation. Gravitation supposedly occurs throughout the universe. When it occurs on earth, it is called gravity. This is the current convention.

No. The force of gravity was considered to be the causative mechanism behind the law of universal gravitation. That made gravity universal too. --EMS | Talk 01:27, 6 September 2005 (UTC)

Basics of gravitation

[as it was placed in the main article and then deleted by EMS]

This section explans in simple terms the physics of gravitation as it has been discovered by Albert Einstein in 1905 [should be 1915] and is still considered the true theory of gravitation. It explains how gravitational force is created and why it looks like attraction between objects.

The phenomenon of gravitation is the result of only two physical phenomena time dilation and curvature of space. It turns out that there is nothing more needed to explain all the gravitational phenomena in the universe. Those two phenomena can be combined mathematically into one geometric phenomenon called the curavature of spacetime but since the curvature of space plays almost no role in gravitation in our solar system (ecxept subtleties of the movement of planet Mercury) we don't need even to consider the curvature of space to explain gravitational force with Einstein's theory.

Time dilation means that the time in any particular point in space runs slower than at a point far enough from any material objects. It means that presence of material objects slows down the rate of time in their vicinity. Time dilation reflects exactly the Newtonian gravitational potential. We'll see later why.

The mechanism of gravitation in the real world is much less mysterious than in Newtonian theory, which many of us may still remember from the high school and which assumed the gravitational force as given by separate "law of universal gravitational attraction". This mysterious "universal gravitational attraction" is the main mystery of Newtonian physics. Einstein eliminated it from physics simplifying physics this way.

In the real world gravity occurs because each physical object contains in itself certain amount of energy and this energy changes with position of the object in space. This amount of energy is expressed by a well known Einstein's equation $E=mc^{2}$ . To calculate gravitational force from this energy one needs to know how much this energy changes when the object containing this energy moves "up" or "down". Direction of the force pushing any object is in the direction of diminishing energy of this object. In free fall in vacuum the object losing this energy is gaining equal amount of kinetic energy since the principle of conservation of energy has to be satisfied exactly and no forces act in vacuum on free falling objects.

The force (as known from high school physics) is the ratio of the change of energy $(dE)$ to the change of position $(dx)$ . So the gravitational force is $F=dE/dx$ . We have to find only the value of $dE/dx$ to derive gravitational force in Einstein's theory. For energy given by Einstein's equation it is (as known from high school math) $dE/dx=(dm/dx)c^{2}+2mc(dc/dx)$ . If the object is at rest $dm=0$ .

As Einstein demonstrated with his equivalence principle and what has been confirmed with experiments $dc/dx=GM/(2cr^{2})$ , where G is Newtonian gravitational constant, M is the mass that causes time dilation in its vicinity, which in turn causes change in speed of light, and r is the distance from the center of mass M to the point in which time dilation is measured. It changes the equation for gravitational force into well known $F=GMm/r^{2}$ , which shows that gravitational force looks as if bodies of mass M and m "attracted each other". In rality it is a force that mass m pushes itself toward mass M with because of the time dilation that mass M creates around itself and causes $dc/dx$ in the equation for gravitational force.

So the gravitational force is exactly as it has been guessed by Newton about 300 years ago. For Newton it was a guess and Einstein demonstrated that it has to be so because of the phenomenon of time dilation. Since the just derived force that is caused purely by time dilation, which is an observational fact, looks identical to Newtonian force and we can have only one force (since otherwise all the object would weigh twice as much as they do) we have to assume the Newtonian attractive force as non existent. Jim 09:22, 16 November 2005 (UTC)

Comment

All that I have to say is that this is totally inadequate. I see no good reason to get more specific than that.

A good reason to get more specific might be to show readers what is inadequate.

Remember that my text is directed to lay people with only high school education who know just simple calculus, which luckily, together with some imagination is enough to understand Einstein's physics. Of course you could also present your version of explanation if you know more adequate explanation. I think that there is no better expalanation but I might be wrong.

I am not involved in Wikipedia to tutor people in GR. If Jim wants to gain a better understanding of GR, he should examine the links and textbooks noted in general relativity resources. --EMS | Talk 17:40, 16 November 2005 (UTC)

I'm grateful for your advice but I studied physics of GR for many years, some at Harvard U, eventually gaining a full understanding of it so your advice is a little late. But I appreciate it anyway.

If you yourself have problems with physics of GR you may just ask me for explanations. Everything you need to know to understand GR happens to be in Einstein's texts but if you missed something, you may ask me. Luckily for you I happen to be involved in Wikipedia to tutor people in GR however I'm rather busy working on my astrophysics degree right now so you might need to be patient. Jim 20:06, 16 November 2005 (UTC)

If your understanding of GR is complete then I would hate to see an incomplete one. In the second paragraph aboove expressing your "understanding" of GR you poo-poo the concept of curvature of spacetime (which is central to GR), and after that rapidly move farther and father away from what GR is about.

Dear EMS, You're playing some kind of an expert on GR and yet you consieder the concept of curvature of spacetime being central to GR. Apparently you don't know that "curvature of spacetime" is just a way of simplifying the math and as such can't tell anything about physics. Consequently can't be central to GR (which is physics, to be sure, not just a mathematical model, as some scientific writers imagine).

If you are so much interested in gravitation you might want to produce some popularization of GR if you have the time to argue how not to write popular atricles on GR. You might start your article with explanaing what most lay people don't know: (i) how gravitational force is generated in Einstein's gravitation, (ii) where the kinetic energy is hidden when the object moves "up" and where it comes from when it moves "down", (iii) why the universe is undergoing accelerating expansion, (iv) what could be GR reason for Pioneers to show "anomalous acceleration". It's only a few words, much less than you already used to imply that my populatisation of Einstein's gravitation doesn't fit your taste. Apparently you don't know the explanations of features of Einsteinian gravitation that I mentioned here but it is not a good reasono to envy those who know them. It would be a good reason to learn some physics and treat Einstein's theory seriously. All the answets are alredy there. Though difficult to notice for scientific writers who delete from Wikipedia everything they don't understand. Jim 20:56, 17 November 2005 (UTC)

The current general relativity article is mostly my own handiwork, and has the tacit approval of the other editors of that page (including Chris Hillman, who is the most knowledgable person on GR in Wikipedia today). I advise that you study it carefully. (i) and (ii) above show that you lack a fundamental understanding of GR, and of how the perception of gravity arises from geodesic motion is a curved spacetime. (iii) is covered under physical cosmology. (iv) is covered in the Pioneer anomaly article. Note that for (iii) and (iv), any additional ideas (unless already properly published) would be original research. --EMS | Talk 22:28, 17 November 2005 (UTC)

P.S. I have dealt enough with GR and my own constantly learning more things about it to realize that assertions of one's own competence in GR are better measures of the person's ego than their competence. --EMS | Talk 22:28, 17 November 2005 (UTC)

Included are such silly statements as the assertion that time dilation gives gravitational potential an "absolute zero" at infinity which Newtonian physics lacks. The truth is that time dilation is just as relative as gravitational potential is, and the "absolute zero" can be defined in Newtonian physics too. Note that this is only one example. Another is the statement that

gravity is exactly as it has been guessed by Newton over 300 years ago.

You say "gravity" instead of "gravitation".

"Instead of 'gravitation'"? Had you already forgotten that your own definition was that gravitational force was "gravity" not "gravitation"? Shouldn't you memorize your definitions before you recommend them to others? Jim 20:56, 17 November 2005 (UTC)

This implies that Newton's force is the same causative mechanism as Einstein's spacetime curvature.

Sorry you goofed, but don't worry, you are forgiven, for your appreciation of science :). Jim 20:56, 17 November 2005 (UTC)

This results listed in tests of general relativity belie this statement.

Perhaps the most egregious thing is that this is not a description of gravitation but instead a novice attempt to explain general relativity. If it reflects your full understanding, then you do not understand GR. If it is an attempt to "dump down" the explanation, then you have done way too good a job of it. --EMS | Talk 21:18, 16 November 2005 (UTC)

Gravitation is a phenomenon, not a mechnism

The reference to force by an anonymous author is inappropriate. That is a description of gravity. In general relativity, for example, gravitation occurs doe to spacetime curvature instead of a force. --EMS | Talk 19:33, 12 October 2005 (UTC)

DREAM COMES TRUE

My life s dream was flying. I never stopped dreaming of it. Not simply to fly but to find the way to the another measurment system (to the another world ) like almost everybody do. Today ,thanks to God , my dream comes true. Our Father that is in Heaven gave me the way . And I am eager to give it to you, and invite you to join me in my very facinating journey to the new world (new measurment system) and you ll never regret it.

ONE MORE STATE CHARACTERISTIC OF THE MATTER

I want to present my discovery about the absolutly different state of a matter (substance) to you. Arm yourself with patience to read more and more times, to go in , to understand , to accept what I m going to present to you . Because my discovery will completely change our understanding about the structure of our Universe ( our measurment system ) from top to bottom. It will give us the solution of the so called black hole phenomenon, and will give an answer to lot more natural phenomena.

As it is known we measure the space by three - dimentional measuring system. Yes the space is three dimensional , but our Universe is four - dimensional.

The space is One with no begining and with no end. and in that common area cold be existing a large number of matter (substances). one of them is our universe ( our measuring system ). An Individual unit with it s own individual life.

You know our universe is extending and we as a part of it , are exposed to some kind of mecanical influence.

To get all these clear , let s begin with the explosion hypothesis (although I am not a supporter of it ). Some part of that phenomenon will bring you closer to the understanding of my discovery and will help you to accept my ideas which I am going to present to you.

I do expect the fact that our universe (our measuring system ) is extanding from some common center (I prefer not to use the word point ) and it is eazy to prove it in practice by the help of spectrum analysis.

Schematically the matter (substance ) of our universe has spherical form, and the matter is placed on theperiphery (outlying area)making kind of outer thin skin (shell) which is extanding periodically ( getting wider , bigger ) and is dicreasing (getting smaller ). Nowaday we are at the stage of extesion with acceleration which we get at expance of differences in innerside and outside pressurs.We can present it diagrammatically. Let s fix some time belt (t-0 ), (mark it ( the time belt) by circle )). On that time belt (circle ) mark some dots (A,B,C.D.E ) galaxies )), C - our earth, is observer .Let s draw between dot C - our earth ,and between other dots - galaxies , a straight lines (CA,CB,CD,CE ). After N time period, in accordance with spherical univers extansion, the fixed points (A,B,C,D,E )-galaxies )) are getting to the t-1 time belt. In accordance with spherical extansion passing the same distance from the relative center. The observer-our earth, will notice that the neighbouring objects (galaxies) are moving away less than those which are farther . By this very way, we can calculate our universe (our measuring system) direction to the center very exactly. I want to mantion that after certain angle of moving away(withdrawal),any such contingency to see more than 80 % of the matter of our universe may be dismissed, because of huge speeds of take away(withdrawal) from the observer. I guess(suppose) that those speeds are higher than the velocity of light. All these said above are only a part of what I want to present to you.

Besides of moving away from each other the celestial bodies are exposed to another influence mechanical size changing in strict proportions according to the mathematical progression. untill now there was not such kind of statement, no one gave or dropped any hint of it.

Father that is in Heaven opened my eyes, opened my ears, enlarged my imagination and gave me the opportunity to see what I have seen. At first everything will seem to you nothing but bullshit, craziness, fantasy.

I don t know what about you,( what will be your reaction, your opinion), but for me it is an EVRICA .

So we are exposed to, for us unnoticable size-changing process which is going on, non stopped, continuous phenomenon. The nucleus is getting bigger at expanse of the kinetic energy which the nucleus is getting during the acceleration.

Take a magnifying glass and look through it. you magnify the objects, things without changing their forms and contents. Like this, the whole matter is getting bigger, wider-extended. The process is continuous (is going on),every next time period the matter is more bigger,wider more extended.

The size changing phenomenon(oscillation) isn t only a process of extansion of the matter but it includes diminutival process also(lessening and narrowing) size changing process(extansion or diminutival process) is depands on in which stage of cycle(oscillation) it is placed ,if the matter is in the stage of extansion-it is getting bigger and wider(mechanically), and if it is in the stage of diminishing (decreasing) it is getting smaller and lesser (mecanically). All I said above is very eazy to prove.

During the extension process it seems to us that the bodies with bigger mass are pulling the bodies with lesser mass (we feel this way). During the diminishing process we ll feel just the contrary.

By all these I want to concentrate your attention on the fact that the Gravitation isn t anything else but the mechanical growth of the matter in mathemathical progression.The mechanical growth we are not capable to see visually, because of it s proportionality, it is all around, everywhere and all embracing.

So our universe is extending -growing-changing sizes, but visually for us the unit (substance) is unchanged - is the same, because of all embracing process of enlargment -extension.

Imagine, that we are unchangable size observers and are standing at any t-0 point of time. Then we ll be able to see the extension of the matter. By the time the matter will become transparant and will vanished from our sight.

The velocity of light is constant only relatively to his measurment system -universe,because it is also, in every next time period getting faster.

There are many other universes(measurment systems) but we are not capable to see them only for now. now we can see only our universe, because of exposure of our molecular construction to general and simultaneously going on extension.

You may ask- what about the wavy phenomena? They also are exposed to a proportional, continuous(going on) extension.

If we ll observe the wave from the fixed unmovable time point, we ll that the wave is growing in the amplitude and is lessening by frequency, and the same step distance is much longer .

MY CONCLUSION

1)So, my conclussion is that the Gravitation mostly is the pressure by the bodies larger by size on the bodies relativly smaller by size, , at expense of bigger extension of the bigger by size bodies in the space. As bigger is the body as bigger is the extension

As big is the radius of the celestial body so is the degree of it s extension.Hence all after coming consequences.

2)Our measurment system-univers, is four dimensional.One more conception like size oscillation (size changing) is added.

The verification of the degree of the extension or compression will give a huge push to our science. It will explain many natural phenomena.

I want to mention, that we are growing to the unbelivable sizes and from the certain critical point the process is just contrary. We ll get smaller, lesser untill certain sizes. And in all these processes strict proportion is observed.

nowaday our univers is in the stage of speeding up, we gettig up our speed. The matter s extensional speed as a rule is lesser, than the speed of the universe-our mesuring system, itself.

So we are in a very dynamic condition.

I hope ,I wish, that using my ideas, my statement in our scince will give us an opportunity to

discover new universes(new measuring systems) and by time to visit them.

Arkadi Vasoyan

arkadiv@012.net.il

Placing "Basics of Gravitation" in the main article

Since nobody presented any argument against my article on how Einsteinian gravitation explains gravitational force I assume that my article is acceptable as an explanation for lay people and so I placed it on the main page. I'm still asking for a critique if someone notices any deviation from the facts. Needless to say that no argument should be suported by faith only but rather by knowledge of contrmporary physics. Jim 23:19, 17 November 2005 (UTC)

Having presented numerous objections above, I am not impressed by this and have reverted your edits. More to the point:

This article is about gravitation in general, NOT general relativity specifically. Kindly note that there is a general relativity article in Wikipedia already (as if that has not already been noted before).
It is not a correct description of general relativity.
The title of the page is not "General relativity" but Gravitation where 16 year old people could go to learn why according to contemporary physics (not necessarily your ideas about it) the weight of a body is $F=GMm/r^{2}$ (which they happen to know from their high school physics). So far you haven't provided this explanation. Do you know how is you going to do it differently than I did? I may wait util you learn how to do it but so far there is no explanation of this trivial fact in the whole Wikipedia (correct me if I'm wrong). Jim 10:06, 18 November 2005 (UTC)
Your equation is Newton's law of universal gravitation, and that is discussed under gravity. The connection between gravitation and weight is discussed in the article on weight, and that is where it belongs. The issue here is much more high-level. I will agree that this article should be accessible to an educated 16-year-old. I will not agree that it should describe weight or go into voluminous details on any one theory. BTW - It also would be nice if what it had to say on GR was correct.
The claim that we see an accelerated expansion of the universe because of dynamical friction is blatant original research.
Why do you think there is such a claim? Jim 10:06, 18 November 2005 (UTC)
If you are not claiming such a connection, then why bring it up in that context as the first thing that you need to study? The implication is especially strong given that the reference to dynamic friction is the only thing in that section. If you did not intend such an implication, you should not have left that section as you did.

My own idea of how to expand this article (and it does need expansion I will admit) is to create one that breifly describes the various dominant views of gravitation throughout history. These would include Aristotle's views of both planetary orbits (and later Ptolemy's model), and the Aristototlian view that the more an object weighs the faster it falls; the observations of and theories of Galileo, Copernicus, Brahe, and Keppler; Newton's theory; and finally GR. Note that each description would be brief and refer the reader to the full articles on the subject. For the GR write-up I would tranfer to here the existing write-up in the gravity article, with the idea of having that become just an article on Newton's theory. Finally, I would rename this article theories of gravitation (replacing the current redirect). I think that having gravitation redirect to theories of gravitation in that case would work quite well. --EMS | Talk 03:40, 18 November 2005 (UTC)

Popularization of physics of gravitation

Dear EMS,

Target of popularization are mostly young people who hope to understand all the physics. For that they don't need to know all the math describing all the physical models that exist. It's enough for them to know the reasons for physical phenomena like gravitation (why things fall).

The simplest gravitational phenomenon is the "gravitational force" (the force that someone sitting on the earth feels as something he's pushing the earht with, or the earth is pushing his butt with). This force is given by an equation $F=GMm/r^{2}$ . Explanation where this force and equation came from, step by step, IMHO should be what popularization of science of gravitation should start with. Not with history of famous people about whom young people interested in physics rather than history might not care at all.

Of course the explanation of this force in "Newton's gravitation" is simple: he guessed it. Nobody before about 1915 seemed to understand the reasons for it.

Einstein knew that Newton's equation was a nearly right model. He tried to guess why it was so nearly right and found the soluton in gravitational time dilation even before he discovered GR. He has understood the reasons for this equation. He was the first human who understood why things fall. What Einstein understood was ... (the stuff you deleted). Using only the concepts that lay people know about and understand (like high school mechanics and calculus) Einstein could explain why this force that is pushing a citizen's butt up has to be almost exactly $F=GMm/r^{2}$ . And a lay person neither needs to know why is called "general relativity" nor is interested in names of models. IMHO, a lay person is motly interested in physics of the pphenomenon. How the gravitatin works. And all we actually know and can tell them about "gravitational force" is what I have written in "Basics of gravitation".

I don't think that living the page blank becaue of your ideas what is the right way of popularizing science is doing Wikipedia any good. "Discussion" of Newton's equation in Gravity page does not explain the origin of gravitational force. Jim 12:21, 21 November 2005 (UTC)

Wikipedia is for documenting human knowledge. So unless a given speculation is well established in the literature, it does not belong in Wikipedia. In addition, there is no such thing as gravitational force in general relativity. Your claims to have studied GR and very much refuted by your apparent lack of awareness of this very fundamental fact about GR. --EMS | Talk 14:38, 21 November 2005 (UTC)

Importance of "dynamical friction" for understanding of "accelerating expansion of the universe"

Dear EMS,

It is such that when people learn about it they start imediately assuming that therefore it might be the reason for observing Hubble redshift while it can't be the reason because of certain properties of Einsteinian gravitation. But those people don't know Einsteinian gravitation yet and so they come up with idea of "tired light effect" and stop thinking. And later it is extermely difficult to convince them that they are wrong. So to know why one has to consider the issu of "accelerating expansion" separately from "tired light" one has to understand why it can't be "tired light effect" and so one has to understand what "dynamical friction" is. Jim 12:21, 21 November 2005 (UTC)

With a topic like this, you either should write on it or not. (Do remember that you can draft an article of section in your user space. You don't need to keep half-editted text in the article itself.)
The expansion of the universe is not technically a case of gravitation. If anything it is anti-gravitation! It therefore should not be covered here, but instead in the general relativity and physical cosmology pages, where in fact it is already covered.

--EMS | Talk 14:44, 21 November 2005 (UTC)

Anti-gravitation? So you think that physicists made a mistake combining attractive and repulsive electricity? There is actually electricity and anti-electricity plus dumb physicists who haven't noticed that the sense of the force makes a fundamental difference not to mention even the magnetic forces calling for the third kind of electricity, perhaps perpendicular one? Luckily we have also a "perpendicular gravitation", already with a name: "dragging of inertial frames". Do you seriously think that it is not technically a case of gravitation? Jim 07:41, 5 December 2005 (UTC)

You keep falling into the trap of treating general relativity (GR) as gravitation. You are not the first and are not the last to do so. However, gravitation is a specific phenomenon, while general relativity is just one of several theorized explanations of it. What I want this article to eventually do is to cover in a quick but comprehensive fashion the history of theorizing about gravitation from Aristotle on down. Maybe I will just hunker down and do that soon. In any case, the expansion of the universe and gravitomagnetism (as "perpendicular gravitation" is properly called) are GR-predicted phenomena, and while they are related to gravitation, they are not gravitation itself.

The thing that bugs me most about your proposed edits is that you want to change this article into a discussion of GR. As I noted above, there already is a general relativity article, and one which is mostly of my own handiwork. So if I thought of this page's subject as being primarily about GR, then I would happily change this page into a redirect to the GR article. I haven't. I will not. And I will revert anyone else's attempt to do so. Note however, that I am happy to have in this article a short presentation on GR with a link the GR article itself. However, equal treatment needs to be given to the other models of gravitation here. I hope that this clarified things. --EMS | Talk 19:14, 5 December 2005 (UTC)

"Massive"

Just thought I'd mention this but it might be misleading to the unexperienced in physics to say "gravity is the tendency of massive objects to attract one another" since people may think massive is in relation to size and not in relation to containing mass/matter. So it might be better to change the text to "gravity is the tendency fo objects which contain mass to attract one another". I know it might be kinda nit picky but there are probably a lot of people who would not initially think of the term massive as having mass.

Hope this helps, I'm new at this so I'm still trying to get a hang of things and so just wanted to point it out.--Kaworuchaos 04:51, 3 December 2005 (UTC)

You're exactly right about "massive" but the main problem here is the general lack of understanding of gravitation among physicists. Even Einstein said that he stopped understanding his own theory when mathematicians started to explain it. So now we have too many opinions on how gravitation should be popularized. It seems that no agreement on it can be reached and opinions of people with more time on their hands prevail. They always have time to remove your correction of their silly statements.

BTW, it is also incorrect to say "attract one another" since the "attraction" is only an illusion. It should be rather "to move towards each other" since this is the only physical reality here, but then people who still believe in "gravitational attraction" put "attraction" back to suggest that "maybe Einstein's theory is not the final word" and "we need quantum gravitation to explain the force of attraction". And then comes a mathematician and says "there is no gravitational force in GR" so apparently the force pressing your butt while you're sitting on the earth is an illusion. You aren't supposed to feel anything. But of course mathematicians are not obliged to know any physics and "force" is a physical idea not a geometrical one (which they would understand if it were). So it is rather hopeless enterprise to try to educate people on gravitation. Most of them (all the mathematicians) don't understand Einstein's theory and still hasn't noticed that in GR the universe can't expand (because of violation of conservation of energy, about which they say it's "OK in GR") and so the whole "expansion" is the same illusion as "attraction" and the same easily explainable (to a physicist at least). But how are you going to convince people that their illusions are not reality if they refuse any rational approach and many of them still believe in supernatural calling themselves "physicists" at the same time? If some of them still believe that planets are actually pushed by the angels since it can't be imagined otherwise? Jim 06:55, 5 December 2005 (UTC)

Please stop -- this really does need to be a redirect, for obvious reasons.

Oh, please. There is a very easy, very simple solution to all this. If there is a need to define the terms "gravitation" and "gravity" and to explain how these terms differ, then this should be done in the article "gravity".

If one has two articles, one called "gravity" and the other called "gravitation", then we will have high-school students trying to add newton and einstien to this article, because they think they're "filling it out with the facts". Which means that someone will have to patrol this article from now until infinity, reverting every silly edit made. I don't know about you, but I've had about enough of patrolling silly edits. It would be much easier to just watch one article, than watching and explaining two. linas 21:41, 8 December 2005 (UTC)

Actually, if someone would "fill it out with the facts" that would be nice. I intend for this to be an overview of the subject, with brief treatments of the major theories from Artistotle on down. So if someone comes along and writes one or two quick paragraph and gravity and GR, with references to the full articles, I will be happy. (If you want to know something that makes me unhappy it is the "gravity" article talking at length about GR. That is not needed there, but this article needs to be fixed up first before that text is removed.) Beyond that, I don't see that this page has any more trouble with silly edits than any of the others. --EMS | Talk 23:28, 8 December 2005 (UTC)

P.S. You should look at the article history BTW. This article tends to have relatively little action in spite of your protest above. --EMS | Talk 23:35, 8 December 2005 (UTC)

OK, I apologize for my rash actions and loud words, I just sort of tripped over this on the way to elsewhere. However, I'm still of the opinion that gravity/gravitation should be one article that explains the differences between the two. This is based on my experience with some of the math articles, on vectors and coord frames, where we have a bunch of inadequate, lacking articles that talk mostly about the same things. Thus, I'd rather see one long article that "talks about it all", than two partial articles. If the one big article gets too long, it can always be split (into two long articles). The stubiness of this one is what prompts my desire to merge.

P.s. re: Aristotle, you may consider creating a History of gravition theories. I notice that Category:History of physics is slowly filling in in a pleasant way. linas 23:31, 9 December 2005 (UTC)

Wikipedia ontology and taxonomy on this article

I have put Gravitation in the "Gravity" category so that it can be easliy navigated to. If you have a cow, we can always just create a Gravitation category. I realize that there there is not a strict parent/child relationship here, but the Gravity category already exists. It is much like the Art/Arts duality I had to merge together: people eventually will be able to figure out the fine distinction, but first they have to find the thing. As you can see, I have also added a "See also" pointer to gravity. -- Fplay 05:10, 24 December 2005 (UTC)

I also suggest that you work out some understanding about this thing:

First things first: Gravitation is not gravity. There is a parent-child relationship here: Gravitation is the overall concept, while gravity is a theory of gravitation. Please, please do not confuse the two. I know that work is needed to sort things out since the gravity article (imporperly) includes a section of GR (for instance) and I apologize for not having found the time to do it yet. As for the portal, there are a few cases where "gravity" is used that "gravitation" would be more appropriate, but overall it is not all that bad. I will try to straighten out the portal's semantics in the coming days. --EMS | Talk 06:23, 21 January 2006 (UTC)

Merge into Gravity

See Talk:Gravity for the merger discussion.