Talk:Gravity/Archive 4

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Contents 1 Gravity and Energy 2 Gravity and Energy 3 Archiving done 3.1 More archiving done 3.2 Still more archiving done 4 Scalar gravity 5 Law of universal gravitation merge 6 Gravity vs. Gravitation 6.1 Comments on portal 7 Poll on Law of universal gravitation merge 8 Massive particles 9 merge or not to merge 10 aether repulsion 11 Bhaskaracharya 12 Gravity at planet centre 13 Vardhu7 comment moved here 14 Second paragraph 15 Reorganisation 16 I think this is not the appropriate quotation 17 I have a problem with a statement and I am removing it 18 Merge Gravitation and Gravity articles 19 Is gee not a vector? 20 Split off Universal Gravitation 21 Fabrizio Bartolomucci? 22 New definition of gravity!! 23 Gravity and accelerated motion

Gravity and Energy

The first sentence of the article states:

"Gravity is a force of attraction that acts between bodies that have mass."

This is not exactly true, is it? Photons are also affected by gravity. shouldn't it be rewritten to something like:

"Gravity is a force of attraction that acts on packets of energy."

This would lead to the following equation:

where,

is an energy packet

is another energy packet

is the distance between the energy packets

is the Planck force

The Planck force is given by:

= 1.21027 × 10⁴⁴ N

GoldenBoar 07:46, 2 January 2006 (UTC)

• I am not qualified to comment on the accuracy of any of this, but I would like to see the opening statements remain in a form that is accessible to the lay reader, and relegate the very technical stuff to later sections, maybe cross-referenced from the opening statements in a kind of "this isn't actually really true; see whichever-section-it-is for a more technical explanation" way. Matt 14:01, 2 January 2006 (UTC).

But ure forgeting mass and energy is the same, soa photon have acctualy a mass cause it has energy, so that statement is still true

Magicmarc: agreed but remember a photon can be represented as a particle or a wave. The only reason we say it has no mass as a model is so that it can be accepted at travelling at the speed of light.

Gravity and Energy

HEEELLLPP!!! PLEASE!!!! I am a newcomer, I need help of unknown origin, and don't know how to go about it. I have made a connection between Newton's, Einstien's, and other's theories and laws, and have theorized. How do I go about,(if possible) using this site to attract attention to assist me in experimentaion of my non-hypothesis of Quantum Gravity. And building the Self Gravitational System/Generator, without someone theiving MY thoughts and running to the patent office. Believe it or not I have found the Railway, if I may, to the substratum of the Universe. And I have no more than a High School Diploma. But the proof has already been published, it is just connecting the dots. I don't want to lay the dots out for the scientific community if I won't get to connect them and be part of stacking the papers. I need a confidential, educated, financial backer, prefferably company based, to endeavor this astronomical advance in the physical understanding of the system of things as we know it. Yet I have now idea how to advertize for my neccessity. Is there any way this site can help me???? Thank you ==

Wikipedia is not the right forum for this endeavour; being an encyclopedia, one of the key precepts is no original research. You should rather try to get yourself published, in Nature, or Physics Letters, or some such.

Urhixidur 19:29, 30 November 2005 (UTC)

Hi, I was wondering if gravity used any energy to attract other masses? If so then where does the energy come from? if not how does it actually attract masses together? Because all I've heard is that its the force of attraction between two or more masses.

Newton's theory of gravity has been superseded by general relativity. Under that thoery, there is no force of gravity. Instead, the tendency of massive objects to accelerate towards each other is called gravitation, and it is due to the way that the masses curve spacetime. In the lack of a force, there is no exchange of energy, as is the case for electromagnetism (in which case the "source" and "sink" of the energies in the electrical charges themselves).

A particle called a graviton must exist as the quantum of gravitational radiation. However, the purpose of the graviton appears to be transmit information about changes in spacetime curvature instead of acting as the gauge boson (or mediator of) gravitation. --EMS | Talk 7 July 2005 14:56 (UTC)

The graviton should exist if modern formulations of quantum gravity are correct. This is far from "a graviton must exist". In fact, there is very little evidence that gravity is quantized at all. Thus, I think your statement is false as stated, and definitely misleading. --D. Estenson II 12:59, July 25, 2005 (UTC)

To answer the original question, where does the energy come from?, classically, the energy in gravity was provided by the universe when the particles were originally separated from each other by the "big bang". This is can be traced to the fact that mathematically, negative force is attraction, energy tends to decrease, and the zero-energy point between two masses occurs when they are infinitely distant from each other.

From the more correct view of general relativity, the energy is an illusion caused by the fact that spacetime itself is not flat. This follows from the idea of curved spacetime and Newton's law of inertia if extended to include a mass in a gravitational field. Since time is taken as a dimension similar to space, "motion" through time contributes to overall motion through spacetime. A particle must always follow the shortest path between two points, and it turns out the shortest path between here-now and here-one-second-from-now is a path which feels to a particle like a downward force. Since gravity distorts lengths in space and time, as "time passes", a mass "feels a force" in the direction of the source of the gravational field. So a mass is mutually attracted by another mass because of inertia and nature of the non-flat spacetime which surrounds any mass. --D. Estenson II 11:11, July 27, 2005 (UTC)

My speculation is that gravity is an effect caused by the spin of the earth around the sun (see Spin (physics)). -- CyclopsX 12:31, 11 July 2005 (UTC)

Archiving done

I have moved most of the previous discussions on this page to Archive 2. The exceptions are the Nigel thread and the one following it.

Hopefully the Nigel thread will terminate soon enough, so that it can be moved to Archive 3. --EMS | Talk 8 July 2005 04:36 (UTC)

More archiving done

The Nigel thread is now archived. Hopefully this will be the end of the housekeeping for a while. --EMS | Talk 05:36, 23 July 2005 (UTC)

Still more archiving done

It is past time to archive the newer part of the Nigel thread. --EMS | Talk 21:14, 24 September 2005 (UTC)

Dear EMS57,

In ignoring the gravity mechanism as verified experimentally, you should be aware of some interest in the spacetime fabric by Professor t'Hooft, sor example http://eskesthai.blogspot.com/2005/08/fifth-dimension-is-spacetime-fabric.html

The difficulty with suppressing a defensible viewpoint by simply refusing discussion (or claiming to disprove it by a bogus claim that 'logic' can prove the moon to be cheese), is that it does not stop progress from being made. Current teaching of general relativity, as causing a flat surface like a rubber sheet to curve into a manifold, is unhelpful to further progress in unifying quantum space with gravitation, since physical space fills volume, not surface area.

Yours sincerely, Nigel

Current teaching of general relativity, as causing a flat surface like a rubber sheet to curve into a manifold, is unhelpful to further progress in unifying quantum space with gravitation, since physical space fills volume, not surface area.

Of course, this familiar image of a curved 2D surface is just an aid to understanding how 3D space can be curved, which can be difficult to picture at first. --noösfractal 17:39, 26 September 2005 (UTC)

Astronaut-physicist-programmer Dr Lunsford has proved that the simplest mathematical system which gives Maxwell’s equations and general relativity is 6 (SIX)-dimensional. Notice that he got it published in a theoretical physics journal last year but it was removed from arXiv.org, since mainstream physics uses only 1, 2, 3, 4, 5, 10, and 11 dimensions. They used to also have 26, but that is replaced by Witten’s string theory breakthrough of 1995, ‘M-theory’ in which 10 dimensional superstrings are proved to have 11-dimensional supergravity as a limit. M-theory is crackpot, Dr Peter Woit says, because it produces no testable numbers. It is defended by the establishment as it involves 6 dimensions curled up into ‘beautiful’ Calabi-Yau manifold, which Woit describes as being mathematically vulgar and ugly. The fourth dimension is necessary to explain why Pi is constant 3.14159265... in maths, because general relativity has volume reduced radially around a mass without affecting circumference, which would increase Pi if there were only 3-dimensions. The radius of the planet earth for example is reduced by (1/3)MG/c^2 in general relativity radially, with no transverse contraction of circumference, so that Pi increases slightly unless you have a 4th dimension so that the 3-dimensions we perceive are ‘distorted’: similarly, a circle (2-d) drawn on the inside of a globe (3-d) has reduced radius, since the radius is longer over the curved surface than a straight line radius. The fifth dimension comes in two ways. First the Kaluza-Klein attempt at unifying general relativity and electromagnetism, which Lunsford shows is wrong in his paper, involved a fifth dimension being added to general relativity. Second, more recent work by string theorists has led to the ‘holographic conjecture’ of t’Hooft, which states the 4-d spacetime of general relativity is a like a 2-d hologram of a 3-d underlying reality. Holography reduces the number of dimensions by 1, and the fifth dimension can be described as a spacetime fabric. By themselves, these mathematical theories have no mechanisms or predictions of a concrete testable support, which is why I’m concentrating on unifying it with my stuff based on some of Catt’s ideas, to get mechanisms and tests. (Lunsford’s 6-d work may however make some testable predictions itself, as it gives general relativity and Maxwell’s equations as approximations to a deeper mathematical system.)

‘With such a dramatic lack of experimental support, string theorists often attempt to make an aesthetic argument, professing that the theory is strikingly ‘elegant’ or ‘beautiful.’ Because there is no well-defined theory to judge, it’s hard to know what to make of these assertions, and one is reminded of another quotation from Pauli. Annoyed by Werner Heisenberg’s claims that, though lacking in some specifics, he had a wonderful unified theory (he didn't), Pauli sent letters to some of his physicist friends each containing a blank rectangle and the text, ‘This is to show the world that I can paint like Titian. Only technical details are missing.’ Because no one knows what ‘M-theory’ is, its beauty is that of Pauli's painting. Even if a consistent M-theory can be found, it may very well turn out to be something of great complexity and ugliness.’ (Dr Peter Woit, ‘Is string theory even wrong?’, American Scientist, March-April 2002, http://www.americanscientist.org/template/AssetDetail/assetid/18638/page/2#19239)

Predicted force strengths and all nuclear particle masses from causal mechanisms

Danny Ross Lunsford’s major paper, published in Int. J. Theor. Phys., v 43 (2004), No. 1, pp.161-177, was submitted to arXiv.org but was removed from arXiv.org by censorship apparently since it investigated a 6-dimensional spacetime which again is not exactly worshipping Witten’s 10/11 dimensional M-theory. It is however on the CERN document server at http://doc.cern.ch//archive/electronic/other/ext/ext-2003-090.pdf, and it shows the errors in the historical attempts by Kaluza, Pauli, Klein, Einstein, Mayer, Eddington and Weyl. It proceeds to the correct unification of general relativity and Maxwell’s equations, finding 4-d spacetime inadequate: ‘… We see now that we are in trouble in 4-d. The first three [dimensions] will lead to 4th order differential equations in the metric. Even if these may be differentially reduced to match up with gravitation as we know it, we cannot be satisfied with such a process, and in all likelihood there is a large excess of unphysical solutions at hand. … Only first in six dimensions can we form simple rational invariants that lead to a sensible variational principle. The volume factor now has weight 3, so the possible scalars are weight -3, and we have the possibilities [equations]. In contrast to the situation in 4-d, all of these will lead to second order equations for the g, and all are irreducible - no arbitrary factors will appear in the variation principle. We pick the first one. The others are unsuitable … It is remarkable that without ever introducing electrons, we have recovered the essential elements of electrodynamics, justifying Einstein’s famous statement …’ D.R. Lunsford shows that 6 dimensions in SO(3,3) should replace the Kaluza-Klein 5-dimensional spacetime, unifying GR and electromagnetism: ‘One striking feature of these equations ... is the absent gravitational constant - in fact the ratio of scalars in front of the energy tensor plays that role. This explains the odd role of G in general relativity and its scaling behavior. The ratio has conformal weight 1 and so G has a natural dimensionfulness that prevents it from being a proper coupling constant - so this theory explains why ordinary general relativity, even in the linear approximation and the quantum theory built on it, cannot be regularized.’

Rueda and Haisch, Physical Review A v49 p 678 (1994), suggested that the virtual radiation of electromagnetism can cause inertial mass, and in Annalen der Physik v14 p479 they do the same for gravitation in general relativity. The virtual radiation acts on fundamental particles of mass, quarks and electrons, which are always charged. It doesn’t ignore all the quarks in a neutron just because they have no net charge. A gauge boson going at light speed doesn’t discriminate between neutrons and protons, only the fundamental quarks inside them. Therefore, the background field of virtual radiation pressure besides causing inertia (and the contraction of moving objects in the direction of motion) also causes gravity (and the contraction in the direction of gravitational fields, the reduction in GR). The force strength for electromagnetism is then naturally related to gravity. Between similar charges, the electric field causing the radiation pressure adds up like a series of charged capacitors or batteries (remember, we’re talking of potential energy difference in volts, not current). In any line, there will be approximately equal numbers of both charges, so the sum will be zero. The only way it can add up is by a drunkard’s walk, where the statistics show the net charge will be the square root of the number of similar charges in the universe. Since there are 1080 charges, electromagnetism will be the square root of this, or 1040 times stronger than gravity. ... http://nigelcook0.tripod.com/

There has been a lot of progress in the past month on this subject.

Science orthodoxy = science

Above is the ‘greatest’ formula in the world, the formula used to keep progress from occurring! If it is not orthodox, it is simply not science. ‘Men are deplorably ignorant with respect to natural things … they must be made to quit the sort of learning that comes only from books, and that rests only on vain arguments from probability and upon conjectures [M-theory].’ – William Gilbert, De Magnete, 1600 AD. - Nigel

Scalar gravity

The added section on scalar gravity was removed for the following reasons:

1. I have not heard of this before. So it probably is original research.
   • The link Introduction to Scalar Gravity is by Paul Bird, whom I suspect is the person behind this new section.
2. It is none the less a speculative theory.
   • The site treats the existing evidence for GR as being questionable, but offers no detailed alternative explanations for its successes.
     • Scalar gravity allows for no deflection of light by massive objects such as the Sun. Other explanations are proposed, but no detailed analysis of them is done.
     • Scalar gravity allows for no non-Newtonian perihelion precession. It is noted that there are potential Newtonian causes for the perihelion precession of Mercury. The author is unaware that the perihelion precession of Mercury has been carefully analyzed, and the issue is an observed non-Newtonian component, as described in tests of general relativity.
3. There is still too much GR stuff in this article for my liking. As this is an alternative to GR, it would be much better being mentioned the general relativity article as one of the other theories. This however assumes that it is even worth mentioning. Also, if it is mentioned there, it must be with a one-line description.

So (as I see it) even if this anonymous poster (most likely Paul) can show that this is not his original research and is of some current or past acceptance in the field of gravitation research, it would at best rate an "honorable mention" on the GR page. However, I will give him credit for a well-written web site, even if I cannot support this scalar gravity or its being mentioned here. --EMS | Talk 17:12, 11 July 2005 (UTC)

Somebody just dropped into WP the article Scalar Gravity, you should watch this one, too. I'm also looking for published papers that can make this topic more than original research. Awolf002 21:08, 5 November 2005 (UTC)

Law of universal gravitation merge

{{mergefrom}} Law of universal gravitation and gravity

This sounds like a very good idea to me. There is not anything more said in that page that is not said here, nor is there really much more to say on it. I support creation of the redirect ASAP. --EMS | Talk 05:36, 23 July 2005 (UTC)

AFAIK, the law of universal gravitation should be a page about a specific theory of gravity put forth by Newton, which was generally regarded as the law of gravity until work by Einstein et al on general relativity. For this reason, these pages should remain seperate. --D. Estenson II 12:53, July 25, 2005 (UTC)

I would be more in favor of that position if the section in this article entitled "Newton's law of universal gravitation" was not larger and more informative than the article Law of universal gravitation. As-is that article is only redundent, and would be better off being a redirect, with the link to it in the gravity article itself referencing the section lower down itself (and I am seriously considering changing that link now, btw.)

I for one think that we need to figure out just what these articles are supposed to be about. My own feeing is that "gravity", being by definition the force hypthesized by Newton that causes gravitation, ought to be uniquely the focus of this article. The only references to general relativity or quantum gravity ought to be in a "status" section wherein the change of paradigm is noted along with the fact the Newton's model continues to be used for "normal" situations since it is much simpler and more than accurate enough. A fuller overview ought to be in an article entitled "gravitation" (which currently is a redirect to this page). However, that should just be a broad brush overview of the field, briefy touching on Newton's theory, GR, quantum gravity, and significant alternative theories. --EMS | Talk 15:04, 25 July 2005 (UTC)

90% of the information in the first two sections, and section 11, should be moved onto its own page, like law of universal gravitation. In fact, a good deal of the total information in the article would be better suited in more specific articles. For example, I think the only equation that gravity should have within it is F=G*m1*m2/r^2. There may be a good argument for keeping the miscellaneous equations near the bottom, but maybe they should be moved to an article such as equations of falling bodies or something.

I agree with you that the article, as it currently stands, seems to lack any purpose focus, and looks to be a hodgepodge of miscellaneous information variously related to gravity. The article should provide an introduction to gravity, giving an overview of what gravity is and how it is used, as well as an overview of its history in science, and brief introductions with links to each of the well-developed theories of gravitation. Everything else is bloat that should be moved to more specific articles or removed altogether, IMHO. --D. Estenson II 10:09, July 26, 2005 (UTC)

I would be happy to see a reorganization of this material. It badly needs it. However, I would not say that this article lacks purpose. If anything it has too much purpose! My complaint is that it lacks a simple, coherent focus. It tries to do too much, and in the end does little of it well. It also jumps back and forth, with standard material interleaved with discussions about various alternatives. Newton's objections is near the bottom while a section on problems with Newton's theory is near the top, etc.

I think that the idea in your last paragraph is good one, and echoes my own call for an overview page. I think that you should go for it. My only request is that you initially develop the new scheme in your user space. This is an effort this is best done in the lack of interference from others, and of necessity must go through an intermediate stage where the pages are all but useless becuase they are between states. --EMS | Talk 19:26, 26 July 2005 (UTC)

I don't know that I am the right person to do this. I have been contributing to wikipedia for only a little more than 1 month, and that's been primarily minor corrections of fact or grammar. Also, I am only a layman's expert on gravity, without the encyclopedic knowledge of the subject that should be required. At any rate, I think I could serve a role in the redesign but not the primary one. For example, I could provide some material from a few books written by Mach, Einstein, Weyl, Pauli, Gamow, and Jammer but most of the information contained within them is too sophisticated for a general gravity article.

Maybe for now, we should discuss the intended scope of gravity and try moving toward that idealistic goal. --D. Estenson II 07:05, July 27, 2005 (UTC)

I was just looking through Gamow's Gravity, and it seems like it would make a good model for gravity, if I can condense each chapter into approximately one section. I am considering it. --D. Estenson II 11:28, July 27, 2005 (UTC)

I advise against using a textbook like that. Wikipedia is a collaboration, and that needs to be respected. I honestly suspect that you would scatter data all over the place with that approach, creating a even worse mess in the process. Instead what is needed is a better organization of what we currently have.

I will give thought to creating a "gravitation" page soon. --EMS | Talk 22:33, 27 July 2005 (UTC)

Gamow's Gravity, at least the one I have, is not a textbook. It is more like a 150 page handbook composed of 10 essays suitable for people at an average level of education. I only mentioned it because the structure of the book, and the order and depth of many of the topics within it, would be suitable for this article. I did not mean to use it as an exclusive source, abandoning everyone else's contributions, or splitting gravity into 10 articles (one per chapter), or some other such nonsense. Anyway, I am a better critic than creator, so I shouldn't be doing any major revisions to the article.

BTW, how is gravitation so different from gravity and Newton's gravitational law that it might need its own article? (Notwithstanding that most of the detailed information about Newton's theory in gravity belongs in Newton's gravitational law.) --D. Estenson II 07:17, July 28, 2005 (UTC)

Gravity vs. Gravitation

To answer D. Estenson II's question above:

gravitation is the tendency of massive objects to accelerate towards each other.

gravity is Newton's theory under which all masses exert an inverse-square law force on all other objects which is proportional to the mass of the gravitating object.

So "gravity" specifically calls for there to be a force acting between objects while gravitation refers to the phenomenon in more general terms. The reason for the distinction is beacuse in general relativity masses are not exerting a force on each other. Instead, the way a gravitating mass bends spacetime causes other object (massive objects, photons, etc.) to accelerate towards it.

This is why an overview article can be written on "gravitation" with a fair part of what is in this article moved there. What remains can then focus on Newton's theory instead of being part gravitation overview and part Newton's theory description. BTW - This means that doing the proposed merge becomes obvious.

This is where we disagree. Where are you getting your definitions from? See, e.g. Merriam-Webster for more widely accepted definitions of gravity & gravitation. Gravity is a much more general term than Newton's specific theoretical formulation, and so those two articles should remain separate. I do now agree, however, that gravitation could be treated more generally than gravity. --D. Estenson II 03:29, July 29, 2005 (UTC)

Those definitions are incorrect. It is obvious that the editor of that dictionary had no idea what they are. In the popular press and for most people "gravity" and "gravitation" are synonymous, and that is what those definitions reflect. I am not concerned with that. Instead I an concerned with how scientists in the relevant fields understand those terms. I think that I was told of the is distinction when I started taking general relativity courses. The books tend to assume it in their titles. See general relativity resources to see what I mean. You can also see gravitation on brainydictionary.com. --EMS | Talk 05:03, 29 July 2005 (UTC)

EMS (and any other interested party), I am trying to write a little user manual on how to use some Portal templates. Unless you or others object, I would like to use the Gravitation portal (it doesn't exist yet) as my example. My idea is to take the lead sentences from selected sections of the Gravity article as content for this example portal. You are welcome to critique whatever you have time for (color selection, layout, images, etc.). This should address some of the issues you are bringing up with the current article, as a side effect. I am not trying to stir up trouble with the specific lead sentences and would appreciate whatever thoughts you have on the layout, etc. If you object strongly to this selection, I will simply choose another example set of content, to avoid conflicts. Ancheta Wis 04:41, 16 August 2005 (UTC)

Hello! I support merging "gravitation" into gravity (v.v. would also suffice, but Orwell should be our guide regarding simplicity): they are synonymous terms for the same concept, and rationales to keep them distinct can only muddy the issue for users. If we want to distinguish Newton's theory of gravity specifically, or force vis-à-vis concept, do so explicitly in the article or as a separate section: e.g., Newtonian mechanics or the like, his seminal work Philosophiae Naturalis Principia Mathematica, etc. Perhaps a request for comment should be fielded? E Pluribus Anthony 13:03, 6 November 2005 (UTC)

Here it is so far:

Talk:Gravity/Archive 4/box-header The first mathematical formulation of gravity was published in 1687 by Sir Isaac Newton. His law of universal gravitation was the standard theory of gravity until work by Albert Einstein and others on general relativity. Since calculations in general relativity are complicated, and Newtonian gravity is sufficiently accurate for most applications, when dealing with weak gravitational fields (i.e., launching rockets, projectiles, pendulums, etc.), Newton's formulae are generally preferred.

Steven Weinberg noted that we could still build a suspension bridge with Newton's laws. Newton's theory is much simpler than general relativity, and used very often, so it is usually taught first. Talk:Gravity/Archive 4/box-footer

---

Comments on portal

First of all, for the caption that goes with picture of the astronaut in orbit: Both the astronaut and the Earth are in freefall. Anytime that you are weightles, you are in freefall.

Secondly, the Einstein Field Equations are solved to find the shape of spacetime in various situations. They do not embody the Equivalence Principle, but intead assume it. --EMS | Talk 03:02, 18 August 2005 (UTC)

---

Better, but you still do not express what the Einstein field equations (EFE) are any where near correctly. Please see General_relativity#The_Einstein_field_equations for a better description of them. BTW, you can just not discuss the field equations: They really are quite arcane and may not be appropriate for discussion in a portal intended for a general audiance. --EMS | Talk 05:15, 18 August 2005 (UTC)

Poll on Law of universal gravitation merge

{{mergedisputed}}

I would like to see this done, and if the only person known to oppose this is Dennis then I will do it. However, it would be nice to see if there is a consensus for or against this. I kindly ask people to state their stand (support/oppose), with a brief explanation. --EMS | Talk 03:40, 31 July 2005 (UTC)

• Support - The content of Law of universal gravitation is duplicated here, and needs to be here. --EMS | Talk 03:40, 31 July 2005 (UTC)
• Oppose -- the law can be stated quite briefly, as it is now, without going into its meaning or interpretation, which the gravity articles delves into at length. If someone is looking for a statement of the law, there's no need to make them wade through gravity. Wile E. Heresiarch 04:16, 31 July 2005 (UTC)
• Support - In "Gravity" the law is close to the top, no need to wade through the article.--Patrick 10:13, 31 July 2005 (UTC)
• Either-way - but i would support merging Gravitational constant into Law of universal gravitation. perhaps both should be merged into Gravity but perhaps not. it's like merging Coulomb's law into Electrostatic force. if Law of universal gravitation should be merged into Gravity, then why not merge Coulomb's law into Electrostatic force? r b-j 02:45, 3 August 2005 (UTC)
• Support, and Coulomb's law and Electrostatic force should be one article too it seems. JabberWok 04:15, 4 August 2005 (UTC)
• Oppose, agree with Wile E. Heresiarch. There's nothing wrong with duplication, we should aim to make information optimally accessible to readers with various interests, both general and specific. -- Tim Starling 05:36, August 16, 2005 (UTC)
• Oppose. The gravity article rambles somewhat. Since the Law of universal gravitation can be stated fairly succinctly, it should be in a separate article. -- Cecropia | explains it all ® 07:26, 3 September 2005 (UTC)

• Oppose, No harm done with two articles, one technical, another generic. -- Md7t 00:20, 10 September 2005 (UTC)
• Oppose, I think that the article "Gravity" probably is too big, I would think that it si better the section Newton's law of universal gravitation go to the the article Law of universal gravitation so that the article gravity go a bit smaller (and leave only the most important part of the section in the article gravity) --Lucinos 20:44, 21 September 2005 (UTC),
• Oppose, Two separate articles are fine. A brief mention of the constant in other articles and a history of measurement and a discussion about whether or not it really is a constant in the other.
• Oppose A technical article conerning this specific topic, linked to parent articles, will keep things discreet for users. Speaking of parent articles: "gravitation" should be merged with gravity (v.v. would also suffice, but Orwell should be our guide regarding simplicity): they are synonymous terms for the same thing, and rationales to keep them distinct can only muddy the issue for users. If we want to distinguish Newton's theory of gravity specifically, or force vis-à-vis concept, do so explicitly in the article or as a separate section: e.g., Newtonian mechanics or the like, his seminal work Philosophiae Naturalis Principia Mathematica (which deals with more than gravity), etc. As well, for instance, a discussion of gravitons would be more appropriate in a 'unified' gravity article (no pun at all intended here :)), not as much in a separate article about the law itself. E Pluribus Anthony 13:03, 6 November 2005 (UTC)

It seems that the opinion is pretty conclusive here, I'll take away the merge suggestion template form the article. — Sverdrup 16:00, 15 November 2005 (UTC)

Massive particles

I saw the recent edit and revert removing and replacing 'massive' and thought I'd add my two cents here rather than muck with the opening paragraph.

The article starts with the line:

Gravity is the force of attraction between massive particles.

The immediate problem is that the word 'massive' carries a more common meaning that is not intended here. Maybe the line could be re-written to end with '...betweent particles with mass.' This does string a few prepositions together, but it's clear. However, the whole thing is also very Newtownian in that General Relativity does not require that both objects have mass. The end of the paragraph gets at this, but I would suggest adding 'Newtonian' or 'Classical' in the first sentence. Jmeppley 05:23, 23 September 2005 (UTC)

Yes, we should have this discussion. I reverted, because the sentence became too general, and would have also covered electromagnetism. In the original, classical definition, Gravity is experienced by an object with mass (Newtonian force). That formula also explains the dependence of that force on the mass of the object creating it (this is just a way to phrase it, since obviously there is a symmetry, here). In Relativity, the "force" is created by the shape of space-time, but again this shape is influenced by the mass/energy of the particle(s) and nothing else. So, we should keep "mass" in that sentence, but it would be nice to rephrase it. Awolf002 11:43, 23 September 2005 (UTC)

"Gravity is the force of attraction between objects with mass"

A possible restatement. Ancheta Wis 07:44, 24 September 2005 (UTC)

merge or not to merge

Either way...please dont change the link again,as i have it hooked to my site--thanks Merging means we lose detail. (unsig: 213.243.146.115)

I'm sorry, you have it hooked to your site? What do you mean?

As for losing detail, that might be true, but wouldn't our readers prefer to read a single article than a number of partisally overlapping articles? And if you'll check out the Law of universal gravitation article, you'll see it contains very little that is not covered in Gravity#Newton's law of universal gravitation, and that this article contains objections to the law that actual law article does not show.

I am not a regular contributor to these articles. I'm sure this topic has sparked intense discussion elsewhere, though. -- Ec5618 08:18, 10 October 2005 (UTC)

One thing it did contain, which is not and never can be here (without a change in the way Wikipedia software works), is six interwiki links.

Another this that was lost was a listing of the law in Category:Gravity, where people aren't going to know that it is covered in the Gravity article, and a listing in Category:Theories of gravitation.

Another problem is that all double redirects have not been eliminated. Gene Nygaard 11:27, 28 October 2005 (UTC)

Definitely merge Gravitational constant into Gravity.

Hello! I support merging "gravitation" into gravity (v.v. would also suffice, but Orwell should be our guide regarding simplicity): they are two synonymous terms for the same thing (and the distinction insignificant enough to keep in two articles, just look at the gravitation article), and rationales to keep them distinct can only muddy the issue for users. If we want to distinguish Newton's theory of gravity specifically, or force vis-à-vis concept, do so explicitly in the article (as is stated upfront in Talk:Gravitation) or as a separate section: e.g., Newtonian mechanics or the like, his seminal work Philosophiae Naturalis Principia Mathematica, etc. Perhaps a request for comment should be fielded? E Pluribus Anthony 13:03, 6 November 2005 (UTC)

aether repulsion

heres a little theory I just thought up, what if matter had the power, rather than of atracting matter, but of reppeling some aether like substance. in the same way that light objects float on water, would it be possible that matter is displaced by the aether being reppeled from a large object, causing it to "float"?, this does not necersarily have to be true, but it is important to take all possibilities into account when you dont know what causes something.

You are hardly the first to think of this. See LeSage gravity. --EMS | Talk 19:52, 7 October 2005 (UTC)

I think the theory is kind of similar, however i was thinking along a different line, imagine say that gravity pushed the oppposite way, and you have an underground lake of water. then some ice blocks, being lighter, comes to the bottom of the lake since the is water is pushing upwards. Now the aether is like the water but it looks like the ice is falling so you asume that is where gravity pulls. correct me if i'm wrong, but having read the article I dont think I found anything about matter actualy acting on aether to push it away, only blocking it.

To quote from the LeSage gravity article:

In this model the gas would normally provide a uniform force in all directions, leading to no gravity at all, except that massive objects block the motion of the gas.

It seems to me that even if you are saying that the aether is repelled by massive objects you are still calling for the same kind of effect: A pressure differential such that objects are pushed inwards towards massive objects. Of course there are issues that you need to deal with here:

• By what means is the aehter repelled?
• How does the aether act on massive bodies so that it can push them? (Do be aware that the original aether was so ephemeral that is exerted minimal forces on massive objects.)
• How is it that this force is proportional to the masses of the objects?

I think that you have some work to so to show that this kind of force can properly model gravitation. --EMS | Talk 01:14, 8 October 2005 (UTC)

Bhaskaracharya

This info might fit under History if you can give some reference to literature or an English translation:

The Law of Gravity - 1200 Years Before Newton

The Law of Gravity was known to the ancient Indian astronomer Bhaskaracharya. In his Surya Siddhanta, he notes:

"Objects fall on earth due to a force of attraction by the earth. therefore, the earth, the planets, constellations, the moon and the sun are held in orbit due to this attraction".

It was not until the late 17th century in 1687, 1200 years later, that Sir Isaac Newton rediscovered the Law of Gravity.

Although Newton is one of the greatest mathematician and probably might has discovered without knowledge og the idea that existed already,unfortunately no one tries to remember Bhaskaracharya

For now I removed that text until we decide what to do. Awolf002 17:33, 27 October 2005 (UTC)

Gravity at planet centre

If one could travel to the centre of a planet, what would the gravitational force be there?

The Talk page is not the place to ask questions of this nature. It is used, ideally, to discuss the article. -- Ec5618 09:26, 28 October 2005 (UTC)

Any questions that promote greater understanding of the article subject amongst editors are, I believe, suitable for inclusion on the talk page.--Light current 16:07, 28 October 2005 (UTC)

Zero, just like inside a hollow sphere, see Divergence_theorem#Gravity.--Patrick 11:00, 28 October 2005 (UTC)

Thank you. I think you are correct--Light current 00:02, 6 November 2005 (UTC)

Vardhu7 comment moved here

  The formula for calculating the gravitational force
between any two objects has been given by Newton as:-

F = GMm / R2

Here G= universal gravitational constant,

M= mass of first object

m= mass of second object

R2= square of distance between the center of masses

But in case of two concentric rings in the same plane ,which have virtual center of masses ,

R = 0

Hence,

F= Infinite.

Thus , it will be impossible to separate them. Any circular disc can be said to be consisting of many such concentric rings. Hence it will be impossible to break such a disc. Similarly, it can also be said be for two concentric spheres , though even after the application of the shell-theorem, we will come to controversial results.Thus, Newton’s law is controversial.

To discuss with me, please mail me at XXX (rm email to evade spam-bots) --Vardhu7 17:57, 8 December 2005 (UTC)--Vardhu7 17:57, 8 December 2005 (UTC)

This argument is a little problematic. The form of the law of gravity that you gave only rigorously (GR, QM aside) applies to two point masses and so cannot be used in the way that you did (beyond that it probably qualifies as OR) Threepounds 07:17, 12 December 2005 (UTC)

I think the error in this argument is "which have virtual center of masses," which seems to use the equivalency of the gravity field outside an extended spherical mass to a point source with the same mass. Since now the argument is about the inside field of an extended mass, this line of reasoning is incorrect. Awolf002 20:36, 17 December 2005 (UTC)

Then what are the laws of gravity to apply inside an extended mass ? why is the max of g for a homogenous spherical mass exactly located on its surface ? sorry for my english and thanx for your time :)

Second paragraph

I'm having troubles parsing the second paragraph. Can the author(s) clarify it? Also the statement isn't quite correct because of relativity (unless relativistic mass is used). Threepounds 07:25, 12 December 2005 (UTC)

We could just revert to an earlier version. Right now, an external review would flag the 2nd para's content as an error. --Ancheta Wis 20:08, 17 December 2005 (UTC)

Reorganisation

When I came to this article a few days ago I found it full of interesting information, but I felt the organisation could be improved. I have therefore reorganised and reordered the material fairly substantially, hopefully resulting in a better flow (though further improvements can still no doubt be made!) I have made every effort not to accidentally lose content in the process, or to garble what was already there. I have made a few additions and changes to the content of one or two sections where I felt competent to do so, but otherwise I have left the information content unchanged. Matt 21:53, 2 January 2006 (UTC).

• Matt, I was following your edits, and I think you did a great job on this article. Thanks! By the way, why wouldn't you open a user account so that we can recognize you every time you're editing something? Yevgeny Kats 22:49, 2 January 2006 (UTC)

I second that!! Awolf002 22:56, 2 January 2006 (UTC)

I think this is not the appropriate quotation

I wish we could derive the rest of the phenomena of nature by the same kind of reasoning from mechanical principles; for I am induced by many reasons to suspect that they may all depend upon certain forces by which the particles of bodies, by some causes hitherto unknown, are either mutually impelled towards each other, and cohere in regular figures, or are repelled and recede from each other; which forces being unknown, philosophers have hitherto attempted the search of nature in vain.

This quotation is saying that Newton wished laws could be found like his laws of motion and gravitation that would explain all of nature. "I wish we could derive the rest of the phenomena of nature by the same kind of reasoning from mechanical principles." Obviously, he here wishes that all of nature could be explained by mechanical principles. He was hoping for quantum mechanics, I guess. He wants to explain why certain bodies repel and attract by mechanical principles. He wants to explain why attraction creates coherent figures i.e. it looks to me like he wants a law for why nature creates solid forms that cohere possibly hinting at atoms and the electromagnetic force.

However, the information surrounding this quote is about causality and Newton's complaints about action at a distance. This is the wrong quote for that and I will be removing this quote and putting in the correct Newton quote.--Voyajer 02:47, 8 January 2006 (UTC)

Perhaps this translation is preferable. I leave it to the original contributor to choose:

Newton himself wrote in a letter to Dr Bentley dated 25 February 1693 (see for example [1], page 302):-

It is inconceivable that inanimate brute matter should, without the mediation of something else, which is not material, operate upon, and effect other matter without mutual contact, as it must be if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe innate gravity to me. That gravity should be innate, inherent and essential to matter, so that one body may act upon another at a distance through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me a great absurdity, and I believe that no man who has in philosophical matters a competent faculty of thinking, can ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial I have left to the consideration of my reader.

--Voyajer 03:56, 8 January 2006 (UTC)

I have a problem with a statement and I am removing it

Similarly, when doing chin-ups, the electromagnetic interaction within the arms' muscle cells is able to overcome the force induced on the body by the entire Earth.

This is a mistaken understanding of bioelectromagnetism. The truth is doing chin-ups is mechanically described by "work" done by the muscles using "leverage".

The electric nature of biological tissues permits the transmission of signals for information and for control and is therefore of vital importance for life. The first category includes such examples as vision, audition, and tactile sensation; in these cases a peripheral transducer (the eye, the ear, etc.) initiates afferent signals to the brain. Efferent signals originating in the brain can result in voluntary contraction of muscles to effect the movement of limbs, for example. And finally, homeostasis involves closed-loop regulation mediated, at least in part, by electric signals that affect vital physiologic functions such as heart rate, strength of cardiac contraction, humoral release, and so on. --Voyajer 03:51, 8 January 2006 (UTC)

• That's as maybe, but it's irrelevant as far as I can see. The statement is just saying that the force exerted by the muscles is due to electromagnetic interaction, isn't it? Are you saying this isn't the case? If it isn't electromagnetic then, as far as I understand it, the only other candidates are gravity, the strong nuclear force, and the weak nuclear force - none of which seems at all likely. (I didn't write the sentence BTW, just curious...)

• • Chin-ups are caused by muscular contractions against bones which provide the base to which muscles attach and also the leverage required to accomplish external movement. The basic action of any muscle is contraction. A muscle fiber contains many myofibrils, which are cylinders of muscle proteins. The contractions of all muscles are triggered by electrical impulses. However, it is not the electrical impulse itself that defeats gravity, it is the contraction of the muscles. The electrical impulses tell the muscle to contract, but the force to overcome gravity is determined by the muscles alone. Everyone has the same electrical impulses, but not everyone is equally able to overcome the gravitational force by bench-pressing the same weight. It is the size and strength of the muscle itself and the strength of the bones that determines whether the person will be able to overcome gravity. If the electrical impulses alone could overcome earth's gravity, then someone without muscles could walk or lift things.--Voyajer 00:38, 12 January 2006 (UTC)

• • • I think we're misunderstanding each other here. When I said that the "force exerted by the muscles is due to electromagnetic interaction" I wasn't talking about the tiny electrical nervous impulses, I was talking about the actual operation of the muscles themselves. What I mean is that, since there are only four fundamental forces known to science, the force exerted by the muscle must, in terms of fundamental physics, ultimately result from the electromagnetic force (since no other candidate seems at all likely). Someone correct me if I'm wrong, but my understanding is that fundamentally it is the electromagnetic force that is responsible for our muscles, bones and bodies even holding together, and for virtually all the activity that goes on within the body, including all the chemistry that actually makes the muscles contract, and so on and so forth. I am assuming that this was the point the original sentence was trying to make. If I am talking nonsense then hopefully someone will put me straight. Matt 01:38, 12 January 2006 (UTC).

Merge Gravitation and Gravity articles

{{merge}} I think the article on Gravitation should be merged into the article on Gravity, for the following reasons:

• The vast majority of the Gravitation article is about the history of theories of gravity, which just overlaps and duplicates what is at Gravity.
• The only other information in the Gravitational article is:
  • The definition: "Gravitation is the tendency of objects with mass to accelerate toward each other". Fair enough, but acceleration due to gravity is extensively covered in the Gravity article so why do we need a separate article to tell us this?
  • The statement: "It is important to note that gravitation is not gravity. Gravitation describes a phenomenon independent of any particular cause. It is possible for gravitation to exist without a force, and according to general relativity, that is indeed the case." Maybe so, but GR is covered under Gravity, and any subtleties about the distinction between gravity and gravitation, with respect to GR or anything else, would more sensibly be included with that material rather than hived off into a separate article. (Incidentally, the Gravity article tells a different story, saying "Although the terms gravity and gravitation are used interchangeably, gravity usually refers only to the gravitational force between the earth and objects on or near it, whereas the term gravitation refers to the property of mutual attraction possessed by all bodies of matter.")
• The word "gravitation" appears throughout the "Gravity" article, most notably in the descriptions of "Newton's law of universal gravitation" and "Einstein's theory of gravitation". If "gravitation is not gravity" then what are explanations of these theories doing in the Gravity article?

Matt 21:02, 11 January 2006 (UTC).

I am staunchly trying to keep these articles seperate. As I see it, this article (gravity) should not mention GR except as an aside (in that it is what has superseeded gravity). Indeed the discussion of theories other than that of Newton's theory of gravity should not be here at all. However, part of what is needed to for someone to do the work of restricting this article to gravity proper and expanding the current "gravitation" article into coherent overview of the major theories (and classes of theories) of gravitation throughout history. If I get the time soon, I will do the work. For now, it is all that I can do to keep there from being backsliding in this regard. --EMS | Talk 22:35, 11 January 2006 (UTC)

In my view most readers will prefer (and indeed expect) to find the chronology of the various theories of the causes, explanations and properties of gravity summarised in one place, rather than split over separate articles. The distinction between gravity and gravitation - which I must admit I was not even aware of prior to coming across the Gravitation article - is something that should certainly be included if it has a sound basis, and sounds like it may deserve better (or at least consistent) coverage, but I think that it should be woven into a single narrative. Of course, if individual sections become too long then, sure, split out the detail to a separate article, but leave a summary at Gravity. Matt 01:14, 12 January 2006 (UTC).

Agree. I agree with Matt, but EMS knows this already. I find the split into two articles to be strange and discomfiting. linas 02:35, 12 January 2006 (UTC)

Matt is on the right track here. It's just that I think that the various theories of gravitation should be documented in the gravitation article, with the gravity article being restricted in scope to Newton's theory. This article also needs to be cleaned up in its use of the terms "gravitation" and "gravity". They are not interchangable, although the difference is subtle. I call on everyone to consider that insititutionalizing the endemic confusion between "gravity" and "gravitation" does nothing to belp either Wikipedia or its readers. --EMS | Talk 00:27, 28 January 2006 (UTC)

• COMMENT there appears to be a strenuous objection on the Talk:Gravitation page on the confusion between gravity and gravitation. —The preceding unsigned comment was added by 132.205.45.110 (talk • contribs) 22:43, 27 January 2006.

Is gee not a vector?

Shouldn't g be in bold or with an arrow on top?

Split off Universal Gravitation

{{split}} Newton's Gravity should have it's own article, this article is too long. If we split it off, we can drastically reduce the size of it to something like the Relativity section.

• Universal Gravitation
• Law of Universal Gravitation
• Newton's Law of Universal Gravitation
• Newton's Universal Law of Gravitation
• Newton's Law of Gravity
• Law of Gravity
• Newton's Theory of Gravity
• Newton's Theory of Gravitation
• Newtonian gravity
• Newtonian gravitation

— These links would then refer to the Universal Law of Gravitation as the main article site. 132.205.45.110 22:42, 27 January 2006 (UTC)

• Oppose I would prefer that this article be shortenned to remove the extraneous (non-gravity) material and overview be placed in gravitation. --EMS | Talk 00:32, 28 January 2006 (UTC)

So, EMS, you are clearly qualified to make the calls here; which of these headings remain in the Gravity article, and which should go elsewhere? If it is simpler for you, you can simply list the numbers or bold them, etc. --Ancheta Wis 01:17, 28 January 2006 (UTC)

1 Overview of the history of gravitational theory

2 Newton's law of universal gravitation

2.1 Acceleration due to gravity

2.2 Bodies with spatial extent

2.3 Vector form

2.4 Gravitational field

3 The Earth's gravity

3.1 Comparative gravities of the Earth, Sun, Moon and planets

4 Mathematical equations for a falling body

4.1 Gravitational potential

4.2 Acceleration relative to the rotating Earth

5 Gravity and astronomy

5.1 Self-gravitating system

6 Practical uses of gravity

7 Problems with Newton's theory

7.1 Theoretical concerns

7.2 Disagreement with observation

7.3 Newton's reservations

8 Einstein's theory of gravitation

8.1 Experimental tests

9 Comparison with electromagnetic force

10 Gravity and quantum mechanics

11 Alternative theories

11.1 Recent alternative theories

11.2 Historical alternative theories

12 Notes

13 See also

14 References

15 External links

Sections 8, 10, and 11.1 are excess baggage IMO as they relate more to GR than to gravity, although GR should be briefly mentioned in section 11.2. Actually section 11.1 and GR should be combined into a single sentance about that "metric theories of gravitation" starting with GR which have superceeded gravity. Quantum gravity also deserves breif mention as an alternative (instead of an entire section). BTW - I may remove section 8 soon, if I can find the time for it. (This is a bit more than a simple removal job, as the Pioneer anomoly text needs to be moved into section 7.2, and I want to be sure that any usable parts of that write-up get transferred to the appropriate GR pages.) --EMS | Talk 05:15, 28 January 2006 (UTC)

Comment. I would like to express again my preference for a single article (don't care whether it's titled gravitation or gravity) which summarises the whole field, from the ancients through to relativity and beyond, with links as necessary to expanded articles about Newton's theory, GR, or whatever other topics merit an individual article.

If the gravity vs gravtitation issue is to be addressed I would like to see upfront a very clear explanation, accessible to the layman, of what the difference is. Most non-specialists do not, I feel, make much of a distinction, so this explanation is essential to make sense of such a split to the average reader. At one time there were two completely different explanations:

• At Gravity: "Although the terms gravity and gravitation are used interchangeably, gravity usually refers only to the gravitational force between the earth and objects on or near it, whereas the term gravitation refers to the property of mutual attraction possessed by all bodies of matter."

• At Gravitation: "It is important to note that gravitation is not gravity. Gravitation describes a phenomenon independent of any particular cause. It is possible for gravitation to exist without a force, and according to general relativity, that is indeed the case."

Based on total ignorance followed by ten minutes' research, I changed the text at "gravity" to read: "In common usage "gravity" and "gravitation" are either used interchangeably, or the distinction is sometimes made that "gravity" is specifically the attractive force of the earth, while "gravitation" is the general property of mutual attraction between bodies of matter. In technical usage, "gravitation" is the tendency of bodies to accelerate towards one another, and "gravity" is the force that some theories use to explain this acceleration." I do not know how accurate this is.

The existing explanation at Gravitation is in my view inadequate, but I do not feel confident enough to attempt to fix it. (The explanation also needs to be at the beginning, not the end). This issue needs to be better explained by someone who understands it. Matt 14:07, 29 January 2006 (UTC).

• Yes, split it. Any wikipedia article with more than seven headings should be split.

Shoefly 03:37, 31 January 2006 (UTC)

• This article is too long. Why not split off Newton? The detailed Newton should go in a subarticle. We should have a Galileo gravity article as well. Zzzzzzzzzzz 20:43, 15 February 2006 (UTC)

Fabrizio Bartolomucci?

Who is Fabrizio Bartolomucci and why is his wave theory of gravity listed under historical alternative theories? Googling "Fabrizio Bartolomucci" doesn't turn up anything relevent or scholarly related to gravity, or perhaps the name was mispelled?

Agreed, this section is not referenced and unverifiable. I will remove it. Also, the user adding it was Fbartolom and so this might also violate WP:VAIN. Awolf002 19:45, 6 February 2006 (UTC)

New definition of gravity!!

Bold text Gravity is a force of oxygen not an attraction of a force!! But if what Fabizio or w/e sad about Gravity is true than man, my Science teacher needs to get a new job or go back to school!...even my dad who was a Science Scholar agrres with me!!!

Please add more if you please!!! - 72.132.56.178 01:00, 14 February 2006 (UTC)!!! Ashley Murphey

Gravity and accelerated motion

Isn't it true that gravity and accelerated motion are indistinguishable? For example, absent all other forces, a rocket accelerating (and pushing against the astronauts' feet) at 9.8 m/s² would have exactly the same gravitational effect on the astronauts, as the rocket being stationary on earth - with the earth pushing against it (and everything else) at 9.8 m/s² (same as saying that the everything is accelerating towards the earth's centre at 9.8 m/s²). In both cases the astronauts would weigh the same. I did not see this mentioned in the article...? Rohitbd 14:12, 16 February 2006 (UTC)

Howcome that gravity is "a force of attraction that acts between bodies that have mass" thats just its behaves. Scientist donnot really know what is it. "We don't really know. We can define what it is as a field of influence, because we know how it operates in the Universe. And some scientists think that it is made up of particles called gravitons which travel at the speed of light. However, if we are to be honest, we do not know what gravity "is" in any fundamental way - we only know how it behaves." - http://starchild.gsfc.nasa.gov/docs/StarChild/shadow/questions/question30.html One question author (All the other scientists that had study gravity and had maked laws of it, it just explaning its "behaves" not what gravity really "is") Let see, try to answer this question-What causes an atom to attract another atom???!!! Could be mass?? Then howcame that the planet Jupiter, hasn't attract to the sun? or may be the planet Earth??

Hello. Please sign your posts with ~~~~. I do agree that we have so far succeeded only in explaining what gravity does or how it behaves, but not "what it is". Every object in space attracts every other. So jupiter attracts the sun just as the sun attracts all other planets. Even human beings attract the earth - just that the mass of humans is so small compared to earth's that when a human falls towards the earth s/he gains much more momentum than the earth. As to why things are in orbit, it is because each planet is moving at just the velocity needed to keep it in orbit. Just as a satellite launched from the earth has to be moving at just (over?) the earth's escape velocity to get into an orbit and once in orbit it maintains that orbit if it maintains its speed. Rohitbd 10:01, 23 February 2006 (UTC)

Under the equivalence principle, what Rohitbd writes is true. However, that is part of the foundation of general relativity in which gravitation is due to spacetime curvature instead of a real force exerted by one massive object on another. There is a difference since in Newton's theory freefall is an accelerated state of motion, while in general relativity it is inertial motion. In any case, this article is about gravity instead of general relativity, which is why is not only is not mentioned by should not be mentioned. --EMS | Talk 21:03, 24 February 2006 (UTC)

24.4.169.214 01:57, 26 February 2006 (UTC)Hi. Im a high school student im intersted in gravity but i still dont understand few thing. The questions that i ask you can you please asnwer them on the level of physics if it is possible? >>Does gravity has an oppositive force or energy between atoms? When you say that "even human beings attract the earth"

Well, I'm not an expert but from what I know, gravity is an intrinsic property of matter. Where there is matter, there is gravity. And gravity is always felt as an attractive force. Rohitbd 12:35, 26 February 2006 (UTC)