Talk:Gravity/Archive 8

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Archive 5 Archive 6 Archive 7 Archive 8

Incorrect drawing in relation to curved spacetime.

The gravitic well, is defined accorded to a point mass at it´s center. There is no point mass, there are gravitic effects within that mass and when you resolve the equations, the attraction becomes equivalent in all directions, away from the center, implying an outwards force, instead of an inwards force. Drawn, that implies that the tip in the center, is higher energeticly then outside the gravitic well. A sinc curve, without the side lobes, is the real curvature. --186.94.187.76 (talk) 18:42, 20 February 2013 (UTC)


"as the agent" ?

"as the agent that gives weight to physical objects"

What does that mean? "Agent" looks like a weasel word to avoid using the incorrect term "force" How about this:

In non-scientific terms, it is most commonly recognized and experienced as the quality of space-time that gives weight to physical objects, and causes physical objects to fall toward the ground when dropped from a height.


50.181.71.228 (talk) 15:34, 28 March 2014 (UTC)

Consider this alternative:
In non-scientific terms, it is most commonly recognized and experienced as that which gives weight to physical objects, and causes physical objects to fall toward the ground when dropped from a height.
Kyle(talk) 07:52, 29 March 2014 (UTC)

Concerning the first sentence of this Wikipedia page.

"Gravitation, or gravity, is a natural phenomenon by which all physical bodies attract each other." I think the first sentence (of the Gravity Wikipedia page) is misleading to someone who wants to learn about gravity. As an aficionado of physics, space science and quantum mechanics, would it not be better to say something like this:

"Gravitation, or gravity, is a natural phenomenon by which all physical bodies attract each other. Many people still mistakenly think that mass attracts mass. While Newtonian physics describes gravity in this way, Einsteinian physics, since 1905, tells us that gravity is actually caused by a physical body traveling through space-time. (In jest, it sort of hurts your head!) Gravity is still one of the most hotly contested and misunderstood scientific theories known to humankind."< ref >The Complete Idiot's Guide To Understanding Einstien, by Gary Moring, 2nd Edition, 2004.< /ref >< ref >The Universe In A Nutshell by Stephen Hawking, 2001.< /ref >

Any thoughts? Mikewest (talk) 18:43, 10 June 2014 (UTC) June 10, 2014

Methinks not. For reasons of style, correctness, and congruence. Cesiumfrog (talk) 00:38, 11 June 2014 (UTC)
(a) Don't use ref tags on talk pages.
(b) You didn't actually change the first sentence, so it can't be all that misleading.
(c) The proposed edit fails WP:TONE, WP:CONCISE, and WP:VAGUE, even before getting into your questionable understanding of your sources. Even reworking it into something encyclopedic—Gravitation or gravity is a natural phenomenon by which all physical bodies attract each other owing to the movement of their mass through spacetime—my understanding is that the fundamental mechanics of gravitation remain unsettled (regardless of sourcing available to individual theorists) and, regardless, that's not clearer than the existing lede, just something that should be explained at length below it. — LlywelynII 23:36, 19 September 2014 (UTC)

Chinese measurement

For comments about the measurement by Tang et al. covered in the Speed of gravity subsection of this article, please see the Speed of gravity Talk page. Mathglot (talk) 06:12, 24 July 2014 (UTC)

Issues with forces definitions.

I have two issues with the third paragraph which describes gravity and the other forces, but I wanted to check here to see what others think first.

0) It is not really fair or accurate to call gravity "the weakest force". There is no invariant way to compare the four forces: they behave very differently on different scales, and they depend on the respective charge values of particles which are affected by them. It would be more accurate to say something like: "because particle rest masses are very small, gravitational effects between individual particles in the same inertial frame of reference are immeasurably tiny".

1) I don't believe it is true that the strong force has limited range. In fact, the strong force is the only force that does not diminish as distance increases (not to be confused with the residual strong or nuclear force, which decays exponentially with distance). Past a certain point, characteristics of particles make it significantly more favorable for the strong interaction to form particle-antiparticle pairs than to increase in distance further; but this isn't the same kind of range limitation as (say) the weak interaction.

I realize all this might be overly pedantic of me, but I think in general the third paragraph could be cleaned up a little. I'll likely attempt this myself if I don't hear feedback soon.TricksterWolf (talk) 21:12, 11 August 2014 (UTC)

In a way, it is being pedantic. We all know that among all the nonzero forces that can be exerted between a given pair of fundamental particles (while isolated together in vacuum at a particular moment), gravity will be the weakest. And we also know that on the larger scales, gravity is the only one that doesn't get cancelled out in practice by other things. These two observations are widely made (and given prominence) in the literature, so they should be mentioned in our treatment of fundamental forces. But by all means go ahead and finesse the wording. (That said, wouldn't you agree the strong force has limited range in the sense that, if you tried to pull a pair of gluonsquarks apart, beyond a certain distance your work will just end up sucking additional particle-pairs into reality, which conspires to let the force slip away?) Cesiumfrog (talk) 00:51, 12 August 2014 (UTC)
I agree completely, Cesiumfrog. I will try to finesse the wording later, but you're right that the observation of gravity being weak between pairs of particles (even the heavy and energetic ones outside of ultra-relativistic frames) is essential to the article. TricksterWolf (talk) 14:43, 12 August 2014 (UTC)
I wouldn't use the wording "in the same inertial frame" to convey the idea of "stationary (with respect to each other)" though. Cheers! Cesiumfrog (talk) 07:24, 13 August 2014 (UTC)

Move to Gravity

I don't have time to go into the whole spiel and actually appreciate Britannica-style formalism, but I'll just take a second to note:

  • Wikipedia's policy is not Britannica-style formalism, but to use WP:ENGLISH WP:COMMONNAMEs.
  • The common name is gravity. Has been for the entire history of the concept, by orders of magnitude. Remains so.
  • The initial rationale for moving most of the page's content to Gravitation was the muddle-headed idea that gravity and gravitation are separate concepts, "gravity" being a Newtonian archaism and "gravitation" being its proper Einsteinic replacement or "gravity" being a force and "gravitation" a tendency in matter.
  • In fact, that is almost precisely backwards. Properly speaking, "gravity" is a quality of matter (its grave-ness: its tendency to sink rather than rise, as opposed to objects possessing 'levity' or 'buoyancy') and "gravitation" (an act of gravitating or tendency to gravitate: to grant gravity) is the force or property responsible for creating such a quality. Newton used both terms in their appropriate places, which is why he talks of objects' gravity but a theory of gravitation (Admittedly in Latin, but y'know).
  • Improperly speaking, they are complete synonyms and already understood as such on this page. Einstein more often wrote 'gravitation' but he was writing in German and using the word correctly to talk about the tendency/force rather than the attribute of particular objects. In English, it's perfectly acceptable that they refer to the same natural phenomenon: 'gravitation' is definition 5 for "gravity, n." at the OED. Our current article leads with the two terms as synonyms and (despite the namespace and its rationale) uses 'gravity' 108 times to 'gravitation'’s 33.
  • Of those two synonyms, 'gravity' is the more common by a wide, wide gulf. All the more so in the professional literature, where Google Scholar returns 2,600,000+ hits for 'gravity' and under 450k for 'gravitation'.

Add my vote to the gravity column when this comes up again, as it has (with 3:1 support) already. — LlywelynII 00:17, 20 September 2014 (UTC)

  • Agree, as per above. Bhny (talk) 04:51, 20 September 2014 (UTC)

References

But seriously... stop using reference tags on talk pages... — LlywelynII

They are usable on talk pages, provided you set the group parameter to the same unique ID in both the reference tag and the reflist template.
David Wilson (talk · cont) 23:54, 13 October 2014 (UTC)

Semi-protected edit request on 29 October 2014

Universe is a gravitotinal pull 92.28.91.195 (talk) 00:00, 30 October 2014 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. Cannolis (talk) 00:06, 30 October 2014 (UTC)

Ancient History section not so ancient

This section states that the events it discusses are from the fourth century CE. However, according to the wiki for the famous Hindu astronomer it quotes from, Bhaskara II, that person was alive during the twelfth century. There is also confusion caused by quoting Bhaskara II as the author of the Surya Siddhanta. The wiki on the Surya Siddhanat does not mention Bhaskara II as one of what appears to be many authors/editors. The confusion may be that Bhaskara II authored a similar work called the Siddhānta Śiromaṇī. Wiki does not confirm that these two writings are one and the same.

Thus, it appears that the entire section on Ancient History is unreliable. The events it discusses did not happen when it says and the quote is either not from the author or not from the piece of work to which the section attributes them to.

174.127.57.218 (talk) 23:39, 4 December 2014 (UTC)

Bhaskara was removed from the article in the meantime. --mfb (talk) 02:02, 24 September 2017 (UTC)

Date for Bhaskara 2 incorrect

Dear moderators,

Following the Wikipedia page and historical references, Bhaskara 2 lived during the 12th century (till 1185), thus making the statement that Newton rediscovered gravity 1200 years later incorrect. Philosophia Naturalis Principia Mathematica was published in 1687.

I would suggest to correct the sentence in the introduction about Bhaskara to something like "more than 500 years later".

Thanks a lot! Keep up the awesome work! Lionel — Preceding unsigned comment added by 2003:4D:EA43:4901:68ED:F0F6:4287:A119 (talk) 16:39, 29 December 2014 (UTC)

Bhaskara was removed from the article in the meantime. --mfb (talk) 02:02, 24 September 2017 (UTC)

Where is the math ?

I am used to physics pages with a bunch of equations and derivations. Yet this page has not 1 at all. I can't even see the basic law. What happened? Are there two pages? One for people that 'read math' and one for everyone else? 77.174.37.89 (talk) 09:28, 3 January 2015 (UTC)

That's a good point, actually. I will add some equations Tetra quark (talk) 16:23, 23 January 2015 (UTC)
Just on general principle that there ought to be a few equations somewhere? EEng (talk) 18:22, 27 February 2015 (UTC)

Dubious claim

Around fourth century CE, the famous Hindu astronomer and mathematician, Bhāskara II in his work Surya Siddhanta wrote: "Objects fall on the earth due to a force of attraction by the earth. Therefore, the earth, planets, constellations, moon and sun are held in orbit due to this attraction." Newton rediscovered this 1200 years later (with the exception of the constellations, which are now known to be well outside the gravitational sphere of influence produced by the earth or sun).

This information seems to be very tendentious and misleading.

  • First, it cites no references.
  • Second, Newton rediscovered this? Even in Newton's epoch when it was known that the Earth was round, no one came to the conclusion the celestial bodies were in orbit due to a gravitational force. Imagine in the fourth century.
  • Third, Bhāskara didn't "discover" that the same way Newton did. He thought that everything was moving around the Earth, which is false. Newton discovered the law of gravitation and used calculus to predict and explain the orbit of the every celestial body close to us.

I was going to remove that paragraph but decided to talk to you guys first Tetra quark (don't be shy) 04:37, 18 January 2015 (UTC)

I'd say remove it. There's certainly at least one blunder in it as it stands at the moment. Bhaskaracharya, or Bhaskara II, lived from 1114 to 1185, so if he was responsible for adding something like the quoted text to the Surya Siddhanta, then it would certainly not be "1200 years later" that Newton rediscovered it. I had very strong misgivings about this when it was added last November, and started to look into it then. However, I was distracted by other matters and never got back to it. According to Wikipedia's article on the Surya Siddhanta, it dates to much earlier than the 12th century when Bhaskaracharya lived, although the surviving version, as translated into English by Ebeneezer Burgess, does date to around that time.
If you do a Google search on "Bhaskaracharya gravity" you will find various contradictory versions of this factoid plastered all over the web, none of them that I could find with a citation to a reliable source, or to the particular place in the Surya Siddhanta where the quotation supposedly occurs. No source is cited for the assertion in Wikipedia's article on the Surya Siddhanta that Bhaskaracharya "modified" it, despite one's having been requested since February 2012. I also haven't been able to verify this, although I have to admit I haven't as yet expended much effort trying to do so. A few web sites attribute the quotation to Bhaskaracharya's Siddhanta Shiromani, rather than the Surya Siddhanta, but, again, none that I could find cites a reliable source, or identifies exactly where in the Siddhanta Shiromani the quotation supposedly occurs.
P.S. Even if something like the quotation does occur somewhere in ancient Indian sources, the version quoted is certainly a mistranslation. All the ancient Indian astronomical systems were geocentric, which is blatantly inconsistent with the statement "The earth &c. are held in orbit ... ."
David Wilson (talk · cont) 12:15, 18 January 2015 (UTC)

As you may have noticed already, I added the citation needed tag. I'm waiting for more people to chime in so we can decide to either leave, modify or remove that Tetra quark (don't be shy) 17:44, 20 January 2015 (UTC)

I've left a note on the talk page of the editor responsible for inserting the information into the article, inviting him or her to join the discussion.
There are several English translations of both the Surya Siddhanta and the Siddhanta Siromani available on the web. I've given a link to Ebeneezer Burgess's translation of the former above. Here's one to a translation of the latter. Here's a link to translations of both works in a single volume. I've performed searches of the full text versions of both the copy of this last volume and the copy of Burgess's translation for the words "attraction", "fall" and "orbit" without finding anything remotely similar to the text quoted in the article. I'm now pretty well convinced that it's bogus.
David Wilson (talk · cont) 10:44, 21 January 2015 (UTC)
Note - see also [1]. - DVdm (talk) 05:50, 3 April 2015 (UTC)
Bhaskara was removed from the article in the meantime. --mfb (talk) 02:02, 24 September 2017 (UTC)

Edit request on what gravity interacts with

The article states the gravity interacts with all particles having mass. According to Professor Matt Strassler, particle physicists do not make that statement. Rather, they say that gravity interacts with all particles having energy. Relativistic mass apparently is not a concept in modern physics.

Relevant paragraph from source:

Throughout this website, what I mean by `mass’ is a property of an object is sometimes called its “invariant mass” or “rest mass”. For me and my particle physics colleagues, it is just plain-old “mass”. The terms “invariant mass” or “rest mass”, used to clarify what you mean by the word “mass”, are necessary only if you insist on having a second, different quantity that you might call “mass”, which is more generally called “relativistic mass”. Particle physicists avoid any possible confusion by never using the concept of “relativistic mass” at all, much less giving it a name.

Photons are massless and yet subject to gravity because of the energy they possess. "Relativistic mass" is misleading and the above source shows several reasons why.

--Luchelibre (talk) 02:30, 23 January 2015 (UTC)

Care to specify where in the Gravitation article that statement is? Tetra quark (don't be shy) 02:46, 23 January 2015 (UTC)
Near the end of the last paragraph of the introduction. "This is the case for several reasons: gravity is the only force acting on all particles with mass" --Luchelibre (talk) 02:50, 23 January 2015 (UTC)
In truth, the entire article needs a adjustment because of this, but I didn't want to ask for the moon on the first go. --Luchelibre (talk) 02:53, 23 January 2015 (UTC)
@Luchelibre: Well, that's indeed a problem. Good catch. Well, rather than saying "gravity interacts with all particles having energy", why not simply say "gravity interacts with all particles"? I'll edit the article now Tetra quark (don't be shy) 03:03, 23 January 2015 (UTC)
Much obliged. I'm looking through the other mentions of mass to see if the word is misleading. Most refer to theories that seem to have only dealt with mass (e.g. Newton), so the change is probably not necessary. Others are more misleading. I'll put up some suggestions and be on my way. Thanks again. --Luchelibre (talk) 03:09, 23 January 2015 (UTC)
The more I look at it, I think this page is better served if I worked to make sure that the Mass and Mass in special relativity pages are brought up to date. All the uses of mass in this article are close enough because of their specific context that I'd be getting a bit close to pedantry. Perhaps the only change I'd suggest is to the original sentence to read "gravity interacts with all particles having mass and/or momentum." That at least reminds the careful reader what he's looking at. --Luchelibre (talk) 04:02, 23 January 2015 (UTC)
@Luchelibre: let me know if you have anything specific you'd like to change Tetra quark (talk) 04:10, 23 January 2015 (UTC)

This problem hasn't been dealt with yet. I agree with the sentiment of the original post, but I do not think the issue has been resolved, either in the ensuing discussion, nor on changes that have been made on the page. To me, the very first sentence of the article, as it currently stands, has a glaring inconsistency:

Gravity or gravitation is a natural phenomenon by which all things with mass are brought towards (or 'gravitate' towards) one another including stars, planets, galaxies and even light and sub-atomic particles.

But light does not have mass! And yet the direction of light is changed because of gravity, as with Gravitational lensing. The difference between the Newtonian and Special Relativity takes on gravity are explained well enough in what follows, but this initial sentence hangs on to the 'mass' idea from Newtonian physics in a way that is not justified and extends it in a way that is not correct (the current sentence strongly implies that light has mass). Okay, I don't mean to sound jerky. Sorry, sorry, sorry. You guys are great. Thanks for giving your time and energy to care for the quality of wikipedia articles. All I'm saying is that someone needs to 1) address the question

https://www.google.co.uk/search?q=light+doesn't+have+mass+but+is+affected+by+gravity

2) digest the answers, like this

The source of gravity in general relativity is an object called the stress-energy tensor, which includes energy density, momentum density, energy flux, momentum flux (which includes shear stress and pressure) etc. Obviously, light has energy, so it acts gravitationally in GR. Since E=mc2, we see that mass contributes an enormous amount of energy - so, massive objects have very strong gravitational fields, so that the other terms are negligible, which is why Newton's law works so well. However, they are there - so, light does have a gravitational field, even though it has zero mass.

— Mark M, http://physics.stackexchange.com/questions/34352/how-is-light-affected-by-gravity

and 3) change this article, especially that opening line. Luchelibre came close when he suggested to say "gravity interacts with all particles having mass and/or momentum". But I don't think that line gets the cigar.

Okay, that's all I've got time for. The future of Gravity is yours. Pigkeeper (talk) 12:51, 20 December 2015 (UTC)

Semi-protected edit request on 23 January 2015

Nevermind, I see the prior discussions about Bhaskara. I recommend removing the entire Ancient History paragraph.

User:Imonomicon (talk) 03:27, 23 January 2015 (UTC)

@Imonomicon: I agree, that should be removed. Tetra quark (talk) 04:09, 23 January 2015 (UTC)
Done  B E C K Y S A Y L E S  06:19, 23 January 2015 (UTC)
As I already indicated above, I agree with the the removal of the paragraph as it stood. None of the three references cited in this edit comes anywhere near satisfying Wikipedia's criteria for reliability, so they have not changed my mind.
I think I have now found the statement of Bhaskaracharya's which was probably the origin of the grossly distorted version quoted in the now deleted paragraph. It's in paragraph 6, chapter 3 of the Siddhanta Siromani (not the Surya Siddhanta). In Lancelot Wilkinson's translation:
"The property of attraction is inherent in the Earth. By this property the Earth attracts any heavy unsupported thing towards it: the thing appears to be falling [but it is in a state of being attracted towards the Earth]."
This concept of gravity appears to be no different from Brahmagupta's, so if any form of the Ancient History paragraph ever gets resurrected, it should Brahmagupta, rather than Bhaskaracharya, who gets mentioned.
David Wilson (talk · cont) 08:22, 23 January 2015 (UTC)

Semi protected now for FOUR YEARS!!! (What the?)

There's no excuse for keeping an article protected for so long. This article reeks of the kind of accumulated errors that would otherwise be fixed up by IPs. Afraid of vandalism? Tough it out. Every other article has to deal with it. When vandalism is done, UNDO IT and move on! Don't go crying for permanent protection you babies. Only a very few special-case articles are actually subject to actual long term "persistent vandalism". This isn't one of them by a long shot. It's time to remove the protection and grow some.

I've got a few good valid corrections to make, but I'm not going to make an "edit request" here on the talk page like a pantywaist. Nor will I be bullied into making to an account and autoverifying just to satisfy you little brats resting on your semi-protection. It's obvious, given the state of the article, that I'm not the only one to refrain.

There is no validity to an argument that a little vandalism four freaking years ago is reason to believe a problem still persists. If there really is persistent vandalism. Prove it. Verify it. Compare it to other articles. Show us before implementing a stinking INDEFINITE semiprotection and then resting on it for FOUR YEARS!

Remove the semiprotection and you will surely get some vandalism, maybe even more than average, but you can deal with it like every other article does. It'll be nothing you mamby-pambys can't handle.

100.0.124.147 (talk) 08:18, 11 February 2015 (UTC)


Not really a valid argument for removal, and in fact, I have a hunch you just want it removed so you can vandalize it. TySoltaur (talk) 00:09, 23 February 2015 (UTC)
I support OP's request. This is supposed to be the encyclopedia that anyone can edit, and I dont see why this page should require a permanent departure from the policies that work fine on other (far more contentious) articles. AnonIPs are also able to help patrol vandalism; TySoltaur I suggest we assume good faith? Cesiumfrog (talk) 08:03, 23 February 2015 (UTC)
Not when one rants like OP did and could not act rationally or civilly. TySoltaur (talk) 21:33, 23 February 2015 (UTC)
Please, let's AGF a little better. You're way out of line to presume like you did that anyone's intention is merely to vandalize. Presuming like that is uncivil by itself, but it's especially outrageous given my actual record, which it looks like you did not review before you spoke. 100.0.124.147 (talk) 05:11, 27 February 2015 (UTC)
Why not simply register an account and then you'd be free to edit? TySoltaur (talk) 08:41, 28 February 2015 (UTC)
It doesn't work that way. IP's are part and parcel of Wikipedia. And it's not about me, it's about all IPs. Don't misdirect the topic, talk pages are for discussion of the article, not for second guessing others' purposes. Get back on topic and AGF. You still haven't made any arguments for protection. Burden of proof is on those who would go against the norm. So, prove it! Give evidence! If you refuse to actually argue a position then at least you can quit the harassment. You haven't even been a contributor to the article. So far on this talk page you've been nothing but a troll. Contribute constructively or go home. 100.0.124.147 (talk) 18:32, 28 February 2015 (UTC)
Calling other people names is not the way to prove you're mature enough for the lock to be removed. It only goes to show reason to NOT remove it. I've been patient, and suggested creating a username so you don't have to worry about pages being locked, but since you would rather rant and rave than just take 30 seconds to register a username, (even though apparently the lock has been removed) I see no reason to continue this discussion with you. Goodbye, and good riddance. TySoltaur (talk) 20:48, 28 February 2015 (UTC)

To be clear, my "passion" displayed in the opening of this section was meant to be a caricature. To state things a little more seriously, the article needs some air. For one thing, it's loaded with four years of accumulated awkwardisms that IP's notice and fix on the fly. Let's normalize the article, let it be subject to the same kinds of follies as every other WP article -- just like every article is supposed to be. 100.0.124.147 (talk) 05:49, 27 February 2015 (UTC)

Well, go fix it. Appears open to ip edits since the 24th. Vsmith (talk) 18:53, 28 February 2015 (UTC)
Doh!  :-) It was done so quietly I hadn't noticed. Rejoice! 100.0.124.147 (talk) 20:10, 28 February 2015 (UTC)

Requested move 17 February 2015

The following is a closed discussion of a requested move. Please do not modify it. Subsequent comments should be made in a new section on the talk page. Editors desiring to contest the closing decision should consider a move review. No further edits should be made to this section.

The result of the move request was: page moved. Anthony Appleyard (talk) 05:49, 24 February 2015 (UTC)

Gravitation → Gravity – I'm not even going to make-up a complicated rationale for this request, as this is all a bit too clear. How can this page not be at the title gravity? We all know that gravity is the common name for this concept, and that our title criteria tell us to use common names when possible (WP:UCN). We've also got WP:CONCISE, which tells us that shorter titles that convey the same amount of information are to be preferred. We've also got WP:NATURALNESS, which favours titles that readers will naturally type into the search box. Does anyone think many people are searching for "gravitation"? I think that's unlikely. Gravity should be the title of this article, and everyone should know that. Let's right this oddity of a wrong. RGloucester — ☎ 02:40, 17 February 2015 (UTC)

  • Support per nom. Couldn't have said it better myself. -- Calidum 03:40, 17 February 2015 (UTC)
  • Support The nom's rationale adds gravity to their argument. Lugnuts Dick Laurent is dead 08:03, 17 February 2015 (UTC)
  • Support English In ictu oculi (talk) 10:44, 17 February 2015 (UTC)
  • Support, I think that "force of gravity" is another way of saying "gravitation" and both are parallels to magnetism, and to the strong and weak nuclear forces. Gravity will do. GregKaye 18:22, 17 February 2015 (UTC)
  • Support of course. It's surprising to me that this isn't at the more natural title. kennethaw88 • talk 02:16, 18 February 2015 (UTC)
  • Support I can't see any issues here.--67.68.161.146 (talk) 03:21, 18 February 2015 (UTC)
  • Support. "Gravity" is simpler, more straightforward, and more communicative. But mostly, it's less hoity toity and that is something WP needs more of!  :-) 100.0.124.147 (talk) 03:25, 18 February 2015 (UTC)
  • Support — More likely search term than "Gravitation", and term conveys the same exact concept. — Confession0791 talk 06:49, 18 February 2015 (UTC)
  • Oppose. FWIW, there is a distinction between these two terms in the technical literature (kind of like how "magnets" and "magnetism" do not mean precisely the same thing). Indeed, the lead of this article used to explain the difference (in different ways over time, if you compare versions from 2007 and 2008 for example). You can also find textbooks that explain the distinction (e.g. the introduction, p20 [2]). Basically, "gravitation" is used to describe the attraction among masses in universal terms, whereas the meaning of "gravity" is usually either the Newtonian force (which is not necessarily present in non-Newtonian theories of gravitation) or to the local inertial force in some frame of reference (especially on the surface of earth, e.g. in geodesy). In this case the gravity is unequal to the Newtonian gravitational force, because the former incorporates the centrifugal acceleration [3]. Finally, "gravitation" is fairly unambiguous, whereas even within the sciences "gravity" has further meanings (including fluid density). Cesiumfrog (talk) 11:52, 18 February 2015 (UTC)
First, you realize that currently, "gravity" redirects here, so you are asking us to create a brand new article. Second, while "gravitation" may be more specific, WP:COMMONNAME says that the more common name should be used. People generally refer to both as the same thing. We can include sections that make a distinction in certain contexts but still use the common name as the article title. --Mr. Guye (talk) 22:14, 18 February 2015 (UTC)
The above discussion is preserved as an archive of a requested move. Please do not modify it. Subsequent comments should be made in a new section on this talk page or in a move review. No further edits should be made to this section.

Gravity does not include centrifugal (pseudo)force.

Inertial resistance to linear acceleration (and centrifugal pseudoforce) have some "equivalent" characteristics to the classical force between masses, but I'm pretty sure it's still debatable as to if and how they might be the same thing.

The Earth's Gravity section asserts, entirely without citations, that Earth "gravity" is the sum of the force produced by actual gravity and the centrifugal (pseudo)force. Is this some kind of unexplained General Relativity based definition that actually equates (vs. "equavalence") C(P)f with the classical force between masses? I don't think so. But if it is, that's a very surprising idea to lay readers and it should be explained (in situ) with reliable references. Instead, I think it's just somebody's odd (WP:OR) and ambiguous definition of terms. As it stands now, the assertion is monstrously dubious and without a single reference. I'll remove the assertion (that Gravity = force between masses + CF) soon unless someone can can make a good argument that I've got it wrong somehow (and can provide references). For now, I'll just mark the need for citations.

Among other flaws, the section is careless in it's disambiguation between surface acceleration, gravity at a spot on the surface, and gravity at a spot in space that isn't rotating with the Earth.

100.0.124.147 (talk) 21:31, 28 February 2015 (UTC)

Steady on. There are multiple concepts of gravity.
  • One model is Newtonian gravity, and you are correct that Newtonian gravity is independent from the centrifugal force, but..
  • We all know that Newtonian gravity is an inaccurate approximation of reality, and that General Relativity is a much better model for gravitation. In GR, gravitation is no longer a force per se, and all inertial forces are equivalent. This works out as saying that the gravitational acceleration that we experience on Earth is the vector sum of the Newtonian component and the centrifugal component.
  • Perhaps you don't care about theoretical models, and you are just empirically measuring the downward force on a unit mass (at some location on Earth's surface). The people who actually perform these measurements are called geodesists. In this case the data you actually measure turns out to equal the total inertial force (again equivalent to combining the centrifugal component onto the Newtonian gravitational force).
Since you asked for references, I'll repeat the ones I gave recently:
  • "the way "gravity" is defined .. is the sum of the two effects" (Note contrast with how Newtonian gravitation is defined.) [4] (Taught at UTexas, US Navy, UNSW satellite navigation lab..)
  • "the value of gravity [is affected by] the Earth's rotation" (page 50) [5] (basic gravitational physics textbook)
Does that help? Cesiumfrog (talk) 23:49, 28 February 2015 (UTC)

Very cool. The "earth gravity" section desperately needs those citations. It also needs to be more clear about when it's talking about what kind of gravity.
I see one quote you give which says "the value of gravity [is affected by] the Earth's rotation". Such passages occur in context in the source and are meaningless if the meaning of that context is not preserved. Does the context really mean to say "the value of free acceleration in a surface frame-o-reference is affected by rotation"? (which is a very classical perspective). Or, does it really mean to say something about the centrifugal pseudoforce in the surface frame being gravity in the GR sense? Such a statement would be very much outside lay expectations and would require very good citations. The fact that such a GR perspective is being used should be clear.
My points are: 1) Be more clear. 2) Cite! 3) Use editorial knowledge to reject bad sources or to properly interpret their context.
I think the article needs to make a much clearer distinction about when it's talking classical and when it's talking GR. It's awfully muddled (and uncited) in that regard as it stands now.
Anyway, I know I made a lot of edits to the Earth Gravity section at once. I know this can be disconcerting. I'll back off a little to give it time to settle.
100.0.124.147 (talk) 00:42, 1 March 2015 (UTC)


Regarding what geodesists do (as you mentioned). It seems you are saying they measure free accelerations on the surface in a surface reference frame. In classical gravity, we wouldn't call that "gravity", but rather the net acceleration in a surface frame. We would "know" that the the net accel is a sum of Earth "actual gravity" (the GMm/r2), the centrifugal pseudoforce, the gravity of the Moon, Sun, bystanders, etc. Forgetting about CF for now, we wouldn't say earth's gravity includes the effects of the Moon, Sun, etc.. Rather we would say the net accleration at the surface includes the effects of the Moon, Sun, etc.. Similarly, we (lay people and those not fully versed in GR) would conceive of "earth's gravity" as the component of acceleration in an unaccelerated frame (such as in space not moving with the surface) which is due only to the Earth's mass. If some models of gravity equate pseudoforces with gravity, it should be made extremely clear when we're talking in those terms and when were not.

But even then, I would suggest that the idea of "gravity being the same as pseudoforce" is perhaps not a firm and fixed idea of gravity and that perhaps it should not be discussed that way in the article. Or if it is discussed, it should be only in it's own separate section. How about that one, eh?  :-) 100.0.124.147 (talk) 01:21, 1 March 2015 (UTC)


I looked more closely at those two refs Cesiumfrog gave above and it's pretty clear that neither of them are calling the centrifugal (pseudo)force the same thing as gravity in a GR sense. All they're doing is using a term of trade, a convention. In the practice of geodesy it seems, or at least in the context of those refs, the term "gravity" is simply the name given to the net acceleration at some point (usually on the surface). It's use implies the sum of the gravities from Earth/Moon/Sun/etc. as well as centrifugal pseudoforce from rotation. Nothing about the way it's used there implies a GR equality of the CF as actual gravity. Similarly, they also don't suggest that the Moon's gravity as felt on Earth should be thought of as "Earth's gravity" just because it affects a measurement of net acceleration on the surface of Earth. We need to apply our knowledge as editors so as to not simply copy things like this out of context if it would change the meaning or make it ambiguous (as it currently does). 100.0.124.147 (talk) 06:20, 1 March 2015 (UTC)

General relativity seems to me to be a red herring here. In my opinion, the main problem with the article's section on Earth's gravity is simply its failure to clearly distinguish between the force per unit mass due solely to the Earth's gravitational attraction and effective gravity, which is the force per unit mass resulting from the sum of the Earth's gravitational attraction and the centrifugal force induced by its rotation. The two physics text-books I checked were also both very sloppy in making the distinction, but when they talked about the acceleration due to gravity on the surface of the Earth, it was clear that they had to mean the acceleration relative to that surface—i.e. effective gravity, and not the force per unit mass due solely to the Earth's gravitational attraction.
The centripetal acceleration of the surface of the Earth varies from a maximum of 0.0339 m/s2 at the equator to 0 m/s2 at the poles, and reduces the strength of effective gravity by an average of 0.0339/π = 0.0108 m/s2. It is clear from section 1.3 of this reference that the figures of 9.78 m/s2 quoted by the article as the "force of gravity" at the equator—which should be "acceleration due to gravity", or "force per unit mass of gravity" at the equator—and of 9.80665 m/s2 as being 5 parts in 10,000 too large for the gravitational acceleration at a latitude of 45° are those for effective gravity, and not for the raw gravitational attraction of the Earth.
It is also not true that effective gravity includes the gravitational effects from the Sun and the Moon. The forces resulting from those effects are tidal forces, which vary in both magnitude and direction at any point on the Earth, with periods of one solar and one lunar day, respectively, and whose maximum magnitudes are utterly negligible in comparison to that of effective gravity (typically, being 0.52 × 10−7 g and 1.1 × 10−7 g, respectively, according to the linked Wikipedia article).
P.S: On performing my own calculations of the magnitudes of the tidal forces, I find that their daily maxima vary quite substantially over longer time periods. The maximum solar tidal force varies from 4.9 × 10−8 g at the Earth's aphelion to 5.4 × 10−8 g at its perihelion. The maximum lunar tidal force varies from 0.96 × 10−8 g at the Moon's apogee to 1.41 × 10−7 g at its perigee.
David Wilson (talk · cont) 16:53, 1 March 2015 (UTC)

I like the way you're thinking. My main point was about being clear as to what's included and what's not included in the term "gravity" whenever the term is used. I mentioned the Sun/Moon/CF as examples of things affecting the net accel relative to the surface that aren't "earth's gravity". Indeed Sun and Moon gravity are super small, but that's not why they shouldn't be included. They shouldn't be included because they're not "of Earth". My other point was that the centrifugal pseudoforce should not be included because it isn't actually gravity. We shouldn't say (or suggest via unclear writing) that any of Sun/Moon/CF effects is included in something called "Earth's Gravity".
Regarding GR as a red herring, yes. As I read it, GR takes a back seat to clarity in what I'm saying. It's just the route toward viewing pseudoforces (PF) as gravity (if I understand correctly). But, the idea of pseudoforces as gravity (and vice versa) is not a settled one (I think). And so, the centrifugal pseudoforce shouldn't be included in something called "gravity".
100.0.124.147 (talk) 05:41, 3 March 2015 (UTC)

We need new lead media

I'm tired of that blurry video. It doesn't look good. I was thinking of something the public would be more familiar with, like an apple dropping from a tree. Tetra quark (talk) 04:52, 3 March 2015 (UTC)

Dubious passage

Currently the section "Gravity and astronomy" says:

The discovery and application of Newton's law of gravity accounts for the detailed information we have about the planets in our solar system, the mass of the Sun, the distance to stars, quasars and even the theory of dark matter.

Two problems with this: (1) as mentioned elsewhere in this article, it does not account for all the detailed information about the planets, in particular about Mercury. (2) Presumably due to grammatical inadequacies, the passage wrongly claims that application of Newton's law accounts for the mass of the Sun, accounts for the distance to the stars, and accounts for the theory of dark matter.

I'll take a shot at revising this -- please consider improving my revision. Loraof (talk) 16:03, 10 March 2015 (UTC)

Re: edit war over Omerbashich material

Re the repeated attempts by User:Inorout over the past week to insert material in the Newtonian section by Omerbashich:

User:Inorout has been indefinitely blocked as a suspected sockpuppet of User:Bosnipedian, (Bosnipedian sockpuppet archive) who was also a promoter of the work of Mensur Omerbashich. The IPs which supported him were also socks. Apparently this guy pops up new socks every month which promote the works of Omerbashich. Heads up: if you see similar behavior in future, report it. Cheers --ChetvornoTALK 21:15, 23 March 2015 (UTC)

Report to whom? Cesiumfrog (talk) 07:51, 24 March 2015 (UTC)
Wikipedia:Sockpuppet investigations. Alternatively, you might contact EdJohnston, the administrator who had him blocked. --ChetvornoTALK 08:03, 24 March 2015 (UTC)

Electromagnetism not relevant to astronomical bodies

Really? And you wonder why Wikipedia still isn't a serious resource. How long has this nonsense been on display? — Preceding unsigned comment added by 188.118.188.201 (talk • contribs) 2015-04-13T14:52:38

The nonsense you would like to see here has never been in the article, and will never be. --mfb (talk) 15:13, 13 April 2015 (UTC)
Notwithstanding the OP's nonconstructive tone (and possible failure to understand the mechanism though which the quality of WP articles improve over time), the lead could be tightened up. For example, "This is the case for several reasons: gravity is the only force acting on all particles; it has an infinite range; it is always attractive and never repulsive; and it cannot be absorbed, transformed, or shielded against" strikes me as being a decidedly woolly statement that says little (it lists both similarities and differences with the EM force). —Quondum 16:09, 13 April 2015 (UTC)
Nonsense like solar eruptions, light, jets from black holes and magnetic field effects (Jupiter on its moons for example), bow shocks, and gamma ray bursts? Your implication is wasted on me. I'm not a crackpot but the claim in the article goes beyond the call of duty. It should be more specific and say that gravity is the dominant force in terms of structure and motion. The passive aggressive note about EM not playing any role is just plain silly and over the top. Gravity isn't the only force out there and gravity doesn't account for every single astronomical phenomenon on every scale. Constructive enough? — Preceding unsigned comment added by 92.252.13.55 (talk • contribs) 2015-04-16T21:36:12
You are arguing against a strawman. No one said electromagnetism would not be relevant at all. The statement is "electromagnetism generally has an insignificant effect on the motion of astronomical objects" (italic added as highlight). All the things you mention are not strong influences on motions of astronomical objects. --mfb (talk) 23:28, 16 April 2015 (UTC)

Reference

Added a published secondary reference for a recent alternative gravity theory. Can I call a vote to keep the content?GravityForce (talk) 11:28, 17 April 2015 (UTC)

I don't see a secondary reference. Keep removed. --mfb (talk) 14:00, 17 April 2015 (UTC)

Gravity vs Gravitation

I think it's important never to confuse gravity with gravitation. Gravity is the hypothetical force that causes gravitation. Einstein's General Theory of Relativity stipulates that gravity does not exist; a theory that has tested positive for 100 years. Whilst gravity may not exist, gravitation certainly does! Equally, I think it's important never to refer to gravitation as a force. Such confusions can hinder one's understanding of this subject. Can anything be tweaked on this page to reflect this? The oracle 2015 (talk) 23:06, 24 April 2015 (UTC)

I tend to agree with the distinction. Dictionaries seem to be of no use here. Linguistically, they are different: there are times when substituting one for the other comes across as obviously wrong. I see very few changes needed, though: I've changed one, and the statement in the lead ("Gravity (also called gravitation) ...") might be rewritten (e.g. to something like "Gravity (the origin of gravitation) ..."). I see no other changes needed. (BTW, one might argue that "gravity" does exist in the EFE, in the form of the Riemann curvature tensor, even if not in the form of a force field.) —Quondum 23:51, 24 April 2015 (UTC)
Although I understand your concerns, I'd like to put in a word for ordinary readers. Gravity is widely referred to as a force in branches of physics outside gravitational physics [6], [7], [8], [9], as well as in physics education and ordinary life. WP is an encyclopedia for general readers, and a big problem in technical articles is use of jargon (WP:JARGON) or words used in a nonstandard manner (WP:TECHNICAL) without explanation, as is being suggested here. I agree with Quondum that the article is okay as it is; its references to gravity as a force are appropriate and in line with usage in general physics texts. I would object to a removal of references to force from the article to try to achieve "politically correct" geometrized language. As Quondum noted, terms in the Riemann tensor can be interpreted as a "force". --ChetvornoTALK 03:57, 25 April 2015 (UTC)
How about then, creating a paragraph explaining in simple terms the differences between gravity and gravitation and then go on to say that the two words will be used interchangeably for the rest of the page due to common usage? The oracle 2015 (talk) 18:13, 25 April 2015 (UTC)
Where (aside from the instance that I pointed out) are they used in a way that suggests that they are interchangeable? Aside from that instance, the whole page seems to use them as different words, albeit subtly. —Quondum 18:52, 25 April 2015 (UTC)
Oracle, do you have sources to support your claim that the two words are used to mean different things in physics? --ChetvornoTALK 20:23, 25 April 2015 (UTC)
@Quondum: Sorry, I haven't read this page thoroughly for some time. Obviously, the first sentence needs a rethink. I'm a bit concerned also that there are constant references to gravitation/gravity being a force, especially early on in the page, yet further down the page it describes the modern/current theory of gravity (general relativity) as not being a force at all.The oracle 2015 (talk) 10:13, 26 April 2015 (UTC)
@Chetvorno: The suffix "ation" to words means "action" so gravitation is the action of two masses attracting one another. Gravity is an old word to describe the downward 'force' of matter on Earth. And in any case, it is widely know within the community how the two words are used so I'm certain that word origins need not to be cited here. The oracle 2015 (talk) 10:04, 26 April 2015 (UTC)
I have no problem with that. It's just that you said at the top "...gravity does not exist", so I thought you were advocating removing the word "gravity" from the text of the article. --ChetvornoTALK 11:48, 26 April 2015 (UTC)
I think we're all adequately on the same page. Let's avoid saying "gravity does not exist", and rather think of it as "gravity does not take the form of a field in which produces a force on a test particle". In general relativity, gravity exists but takes the form of how space shapes itself around its content. I'm comfortable with rewording sensitive to this idea, as well as making the distinction between "gravity" and "gravitation" clear as described by The oracle here. As I said before, already I do not see much conflict with the existing content, but no harm in going through the article carefully and being precise. —Quondum 14:18, 26 April 2015 (UTC)

Gravity, the hypothetical force behind gravitation, does not exist according to general relativity (the current and most accepted theory of gravitation). Gravity, when used to mean gravitation, exists in that it keeps our feet on the ground and is ultimately the creator and powerhouse of the universe. The opening sentence "Gravity (also called gravitation)" is untrue but the reverse is certainly true in that gravitation is often called gravity. The oracle 2015 (talk) 17:59, 26 April 2015 (UTC)

Don't get too particular about the use of words until you have proposed a clear alternative. Until then, we need to keep using "gravity" and "force" to have a broad meaning, especially insofar as we want to describe general relativity. We can't just say "gravity doesn't exist in general relativity". In the broader sense of the word "gravity", it does exist and is described by general relativity; it just does not take the classical form. As I've pointer out, the Riemann curvature tensor describes a real-world quantifiable phenomenon, and can be called "gravity". It is a tensor field, in exactly the same way as other fields such as the electromagnetic field is a tensor. And just like the electromagnetic field, it also has a source (the stress–energy tensor in place of the four-current tensor). Just like the electromagnetic field results in to electromagnetic effects, the Riemann curvature tensor (gravity) leads to gravitational effects (gravitation). So stop saying that gravity doesn't exist according to general relativity in a sense distinct from gravitation. I have no issue with "gravity" meaning the curvature of space–time, though I would like us to clearly qualify the term "force" as being rather loosely interpreted. —Quondum 18:34, 26 April 2015 (UTC)
I agree. By the way, if you wanted to be equally "politically correct" you could make a similar argument for other forces. There is no such thing as "force" in quantum mechanics. When a hammer hits a nail, what's really happening is the atoms in the hammer are exchanging virtual photons, which carry momentum, with atoms in the nail. When a magnetic field rotates the armature of an electric motor, the electrons in the armature winding are really exchanging virtual photons with the stator winding. Newton's law, Coulomb's law and the Lorentz force law are all false, approximations of underlying quantum equations which don't include "force". Shall we go on a mission to eliminate mention of all these "hypothetical" forces from Wikipedia articles, and replace the word "force" with more scientifically correct language, something like "quantized energy exchange by virtual subatomic particles"? --ChetvornoTALK 04:17, 27 April 2015 (UTC)
One can not compare gravitation to "other forces" because gravitation isn't a force, it isn't caused by a force and it has no force carrier. The oracle 2015 (talk) 20:58, 27 April 2015 (UTC)
How about then, drop "(also called gravitation)" from the opening sentence then the correction is made. And maybe raise the differences between gravity and gravitation in a new 2nd chapter? The oracle 2015 (talk) 20:58, 27 April 2015 (UTC)
I'm not objecting to the suggested change, though we do need to define gravitation in the article, since Gravitation does redirect there. I do object to your failure to take note of what is being said. —Quondum 21:19, 27 April 2015 (UTC)
How about a brief initial section after the intro explaining that gravity is not a force, but the result of free particles moving on geodesics in curved spacetime, but that it is often referred to as a force outside relativity physics? I think that is all that is needed; the article doesn't need to be reworded. I would not object to including a statement that some relativity authors avoid the word "gravity" and instead use "gravitation". I suspect that is all that WP:RELIABLE SOURCES are going to support; I doubt sources can be found that say that those two words actually mean different things in physics. --ChetvornoTALK 22:55, 27 April 2015 (UTC)
How about something like this:
Terminology
Although it is referred to as a force in other branches of physics, according to the General Theory of Relativity gravity is not actually a force. The acceleration of a falling body in a gravitational field is not caused by a force acting on it, but is due to the fact that the body follows a geodesic path in the curved spacetime geometry. For this reason in gravitational physics terms like force of gravity or gravity, are often avoided, and the term gravitation is used instead.
--07:39, 28 April 2015 (UTC)
Good but it maybe a little technical so early on in the article. How about something like this;
Gravitation describes the natural tendency of masses (and indeed all mass/energy) to attract one another. Gravity, in common usage, means the same although in physics, gravity refers to the hypothetical force behind gravitation. The oracle 2015 (talk) 10:24, 28 April 2015 (UTC)
I'd rather use the phrase "gravitational field" in place of "gravity" the sense meant by The oracle. I (and I'm sure many others) consider the term "gravity" to have a broader meaning, in essence the mechanism behind gravitation (what ever that is, not necessarily a force). To make a statement as suggested about the term "gravity" would probably be WP:POV: speaking about only one particular interpretation by some people. —Quondum 13:59, 28 April 2015 (UTC)
@Oracle: There are innumerable general physics textbooks that call gravity a "force", so if the article calls it a "hypothetical force" (i.e. not a force) then the article will have to explain why. I think it would work better to simply explain the terminology issue forthrightly, up front, rather than mystify readers with awkward syntax that avoids the words "gravity" and "force". --ChetvornoTALK 16:20, 28 April 2015 (UTC)

@Quondum:Would you check my proposed chapter again please as I thought I kept the definition of the word gravity as being broad? The oracle 2015 (talk) 18:02, 28 April 2015 (UTC)

Sorry, I am being brief and rushed, probably not doing the question justice. You mean "gravity is not actually a force field". I'm not entirely comfortable with the concluding sentence ("For this reason ..."), but I tend to agree with Chetvorno that to launch into explanations like this early might be confusing. There might be ways to word it to sidestep the issue. —Quondum 04:29, 29 April 2015 (UTC)

@Chetvorno:I think it's okay for simplified text books to describe gravity as a force for the subject of gravitation on Earth or when talking about pre 1915 gravity theories. After all, we still use the Newton (the SI unit for force) to measure gravitation on Earth. Text books that otherwise describe gravitation or gravity as a force are obviously wrong. And please, I don't want to mystify readers and I certainly wouldn't want to mislead them to believe gravity to be a force. The oracle 2015 (talk) 18:02, 28 April 2015 (UTC)

But if all a reader has read previously about gravity is those "simplified" textbooks that say gravity is a force, and then he begins reading this article and finds that there is no mention of "gravity" or "force" except for your cryptic statement calling gravity a "hypothetical force", how is he going to feel? Mystified. --ChetvornoTALK 21:48, 28 April 2015 (UTC)
I think keep the word gravity for obvious reasons, just don't mislead the public in to believing gravity to be a force. It is 100 years this year since the realisation that gravity is not a force. It would be a discredit to Wikipedia to knowingly leave in untruths and inaccuracies. The oracle 2015 (talk) 08:03, 29 April 2015 (UTC)

Theory of Everything

In the 3rd paragraph and in the last section in general relativity, the article states that general relativity isn't compatible with quantum mechanics. Can anyone expand on this to explain why this is a problem? I see no reason at all why gravity has to share a theory with the strong, weak and electromagnetic forces. The oracle 2015 (talk) 09:14, 30 April 2015 (UTC)

At least some mention giving an intuition about the incompatibility would be good, though I'm not the person to do it. In essence (and the problem becomes extreme at the Planck scale, for example with a Planck-mass black hole), QM demands that spacetime becomes a superposition of different curvatures: exactly where the black hole is is not knowable. This superposition is not compatible with GR, which describes the spacetime as a manifold. Trying to find a middle road of compatibility requires, at the very least, a modification of GR, and an incorporation of spacetime geometry variations into QM. —Quondum 13:53, 30 April 2015 (UTC)
Are you certain QM demands this? I Can't understand why there should ever be a superposition of different curvatures of spacetime, even in a plank mass black hole. After all, curvatures of spacetime don't posses wave properties do they? The oracle 2015 (talk) 16:51, 30 April 2015 (UTC)
Doesn't it stand to reason? It is the usual Schrödinger's cat problem. The mass distribution determines the geometry of space; the mass distribution is in a superposition of states, ergo the geometry of space is in a superposition. You can't consistently find some single geometry "shared" between all quantum superpositions. —Quondum 19:01, 30 April 2015 (UTC)
Personalally, I think the Schrödinger's cat problem is stuff of fantasy so I don't believe mass distribution can be in a superposition of states. The cat is either dead or alive, even before it's observed. The oracle 2015 (talk) 08:30, 1 May 2015 (UTC)
In the absence of any real prospect of there ever being a positively tested "theory of everything", is it agreeable that paragraph 3 should be removed or demoted to a lower position on the page? The oracle 2015 (talk) 09:58, 1 May 2015 (UTC)
If you feel that (that Schrödinger's cat is in a deterministic state), you're in direct conflict with experiment and quantum mechanics in general; yours would have to be classified as one of the most extreme forms of the Copenhagen interpretation. The superposed state of small "cats" has been demonstrated directly in the form of large molecules. If you only accept the smallest versions (e.g. an electron taking two paths), you still end up with the theory becoming inherently approximate (i.e. incomplete). But you're in good company: Roger Penrose's proposal is that when the gravitational energy difference between two states (and hence the geometry of space differs) on the Planck scale, that an objective collapse occurs. This does not fully solve the problem at small scales, but would prevent substantial differences of geometry being superposed.
As to the third paragraph of the lead's mention of the problem of producing a theory of quantum gravity is notable, and I think demoting it out of the lead would not be appropriate, notwithstanding your pessimism about future theoretical progress; I'm not sure why you should feel that there is "no real prospect". This is a point of major significance with respect to gravity. The point about the graviton is completely separate and more hypothetical, and does not necessarily belong in the same paragraph. I would not object to that sentence being removed from the lead. —Quondum 14:15, 1 May 2015 (UTC)
Mass distributions can be in a superposition - every double-slit experiment with massive particles shows that. So how does spacetime geometry look like? We cannot measure the gravitational attraction from single atoms, of course, but it is a fundamental problem. --mfb (talk) 15:51, 1 May 2015 (UTC)
@Mfb: The double slit experiments involve propagated particles. Propagated particles lose all properties of matter and adopt wave properties from the time they are emitted until the time they are absorbed. How do propagated particles (waves) compare with the geometry of spacetime (caused by the uneven distribution of particles)? The oracle 2015 (talk) 16:04, 1 May 2015 (UTC)
@Quondum: The thing is, if you want to observe a particle to find out information about it, the particle has to interact with other particles in order to convey the information you seek. This involves propagating the particle or propagating a particle at it. Simply 'observing' a particle can change it's properties so we rely on probabilities. There's nothing magic about it; there's certainly no 'cat' in two simultaneous states of mortality. An electron doesn't take two paths (as in the double slit experiment). The electron ceases to be an electron between the times of emition and absorbsion. The electron becomes a wave. The oracle 2015 (talk) 16:31, 1 May 2015 (UTC)
Well, then, you are admitting that Schrödinger's cat exists in a superposition of states and denying it in the same breath. You can't have it both ways. Are you familiar with the quantum eraser experiments? These demonstrate that a system does not (magically!) decide between being a particle and a wave; the simultaneous states of mortality (if that is what you want to call it) are an unavoidable conclusion. Anyhow, this is not the place to be pontificating on the merits of any particular interpretation of QM. The problem of unification of GR and QM is notable and widely recognized. Whatever your personal opinions about the validity of QM interpretations, the general point that the two most successful theories of physics are considered incompatible in their current form does belong here. —Quondum 16:58, 1 May 2015 (UTC)

I don't believe the Schrödinger's cat problem, no. And a quanta is never a wave and a particle at the same time. A particle is obviously extremely small and indivisible. When propagated, the particle becomes a wave, a two dimensional entity with the diameter equal to it's wavelength and inversely proportional to it's frequency (or energy). If an electron is emitted at the energy of 100MHz for example, it will cease to be an electron and become a wave with a diameter of 3 meters. Plenty wide enough to penetrate both the double slits at the same time.

My original query was to ask why GM and QM not being compatible is a problem. I Still don't see that it is. The oracle 2015 (talk) 19:26, 1 May 2015 (UTC)

I'm going to sidestep the cat discussion as being a side-track. GR and QM are incompatible is not a problem to the article, but it must be mentioned: it gives the significant information that GR, despite having superseded the Newtonian picture as being far more accurate, it is known to be a theoretically incomplete description of space–time. Basically, we're dispelling the perception that GR is considered to be a candidate of the "correct" theory. —Quondum 21:21, 1 May 2015 (UTC)
But to explain to the reader why GM and QM are incompatible, would it be correct to say that where GM predicts singularies, QM predicts a sphere of maximum density? The oracle 2015 (talk) 08:16, 2 May 2015 (UTC)
I'm not too sure that QM does predict "a sphere of maximum density". In fact, we can probably say that in situations like this (extreme spacetime curvature), QM does not make any specific prediction, because QM is formulated in flat Minkowski space. I'm not sure that we need to explain the predictions of QM, or the reason for the incompatibility, to include a statement that they are incompatible. Whatever we say should be sourced, though. —Quondum 14:31, 2 May 2015 (UTC)
I've added a little in the lede a little about where GM and QM clash. This is according to this article on singularities and http://io9.com/why-cant-einstein-and-quantum-mechanics-get-along-799561829. I've not cited the edit because doesn't Wikipedia discourage the use of citations in the lede? The oracle 2015 (talk) 09:28, 3 May 2015 (UTC)
I have removed it—not a wp:reliable source. - DVdm (talk) 10:00, 3 May 2015 (UTC)
I think the immediate removal was too extreme. Citations are not always necessary in the lede, wp:lead, and you could have just inserted a 'citation needed' pending removal. And could you explain why the sources were unreliable as you conveniently left that bit out? The oracle 2015 (talk) 10:55, 3 May 2015 (UTC)
Your edit didn't make much sense, so putting a 'citation needed' wouldn't help in this case. Why the source is not reliable is explained at large at wp:RS—see for instance WP:USERG. Furthermore, the source doesn't even directly support your edit. It looks like you synthesised it—see wp:SYNTH. We can of course say something about the GM/QM clash, but, as user Quondum already said: "Whatever we say should be sourced, though." That's how Wikipedia works. There is no room for our own interpretations of blog stuff here . - DVdm (talk) 11:16, 3 May 2015 (UTC)
That's a better explanation, thank you, although I hope you weren't implying that I have any connection to the webpage I cited. My last edit may need putting a different way but all what I said is also said and cited in other Wikipedia articles; Gravitational singularity and Quantum mechanics are the ones I was thinking of. To be honest, the edit is not hugely important anyway but to state GM and QM are incompatible without giving a reason why is a bit open. The oracle 2015 (talk) 12:04, 3 May 2015 (UTC)
I agree that the lack of some background about the reason that GR and QM are incompatible is not very satisfactory, but putting in some heuristic argument to fill the gap is worse. The incompatibility is truly fundamental, and has little to do with the uncertainty principle. In Gravity § Gravity and quantum mechanics the argument is put vaguely, though I suspect that the existing reference (Randall) does no better: it is written as popular science, and may not say much concrete. What the lead can do is to take some information from the content, which says that "it was realized that general relativity is incompatible with quantum mechanics". —Quondum 15:12, 3 May 2015 (UTC)

How about then just adding a line to say at what point GM and QM are incompatible rather than let the reader believe they are generally always incompatible? Would it be fair to say that GM and QM are compatible down to plank length? Or that they become incompatible at super high densities like in black holes? The oracle 2015 (talk) 12:27, 4 May 2015 (UTC)

We need something that we can verify in a book, so we can stick the reference to the text. That should be fairly easy to find... - DVdm (talk) 12:48, 4 May 2015 (UTC)
We already have a cited statement in the body of the article about this. Thus we can say in the lead that it is accepted that GR and QM are not mutually consistent (or whatever summary works for the cited point), without further citation. —Quondum 17:44, 4 May 2015 (UTC)
However, if someone can find a reference that isn't a popular science book, that would be good ... —Quondum 17:46, 4 May 2015 (UTC)

Causal definition of Gravity [not observational as it is on the intro]

Gravity is the resistance of bodies to the curvature of space-time and it's displayed as acceleration (causal definition).

by Chromodynamic — Preceding unsigned comment added by 2.84.216.225 (talk • contribs) 20:07, 21 June 2015 (UTC)

Why is this page locked??

— Preceding unsigned comment added by 182.249.169.9 (talk • contribs)

  • 15:07, May 21, 2015 EdJohnston (talk | contribs) changed protection level of Gravity‎ ‎[edit=autoconfirmed] (expires 20:07, 21 August 2015 (UTC))‎[move=sysop] (indefinite) (Unsourced changes)

That's why. — Confession0791 talk 07:55, 26 June 2015 (UTC)


gravitational wave field radiation

All four forces are expressed as field radiation, thus we shall update the intro:

Gravity, gravitation or gravitational wave field radiation is a natural phenomenon.... — Preceding unsigned comment added by 2.84.216.225 (talk) 17:53, 4 July 2015 (UTC)

Whatever you mean with "field radiation", it is not true. --mfb (talk) 06:15, 5 July 2015 (UTC)

Second paragraph:

If gravity is not a force then what causes the object to move (fall) in a straight line through curved space-time. Isn’t curvature just a bent path in the absence of any force which neither can deliver / give force nor has the power to stimulate an object until and unless there is an external unbalance force acted upon it.

Therefore the word “consequence” in the second line is not enough to comprehend gravity described by Einstein without referring to the source of momentum. 162.157.210.127 (talk) 05:57, 20 July 2015 (UTC)Eclectic Eccentric Kamikaze

Do you have an expectation that a couple sentences should be "enough" explanation for anyone to comprehend General Relativity? (And why do you think momentum is related?)
FYI, have you ever played with an accelerometer? It provides concrete measurements that the free-falling object experiences the absence of any real net force, and that "at rest on the earth's surface" is not an inertial frame of reference; the inertial frame is the one where the "free-falling object" is stationary (and earth's surface is accelerating). This is only the starting point for GR.. (really you also want to be conversant both with four-dimensional tensors and differential geometry..) Cesiumfrog (talk) 11:49, 20 July 2015 (UTC)

Accelerometer isn’t a natural or a single object which can detect its own acceleration by the virtue of its name but it is its internal mechanism which may or may not report acceleration depend upon its status (static or dynamic). Since, all objects free fall at the same rate of acceleration therefore the Matryoshka Doll parts of accelerometer which are responsible for producing signal losses contact with each other as gravity accelerates them equally and hence reports zero acceleration. Further, are the foundations of all buildings wrongly designed in Newtonian mechanics if accelerometer registers 1g upward on the surface of earth. Similarly, if Einstein’s “g” (rocket, elevator and gravity) is more natural then why Newtonian “g” is still applied in many engineering designs.

Neither object impels itself to move nor a curved space-time tells object to move in the absence of any force therefore I was just thinking that doesn’t curvature controvert the law of inertia e.g. if an object stays at rest on the curvature then shouldn’t it maintain its rest position instead of free falls (not caused by a force) in natural motion along a geodesic through curved space-time (just a path not source of generating motion) - my last reply — Preceding unsigned comment added by 162.157.210.127 (talk) 19:08, 21 July 2015 (UTC)

You are reasoning here about the fundamentals of the content of the article, making it an academic discussion about content and not about how the article can best reflect sources; you also seem to be missing the point of Einstein's equivalence principle, which is a well-established and documented. Consequently, this is not the place for this discussion. See WP:TALK#OBJECTIVE. —Quondum 04:30, 22 July 2015 (UTC)

Earth's gravity

This section has this as the first sentence. "Every planetary body (including the Earth) is surrounded by its own gravitational field, which exerts an attractive force on all objects." This is utter nonsense. Gravity does not have an attractive force. The warping of space pushes an object down towards the Earth. I know the topic is complicated and I don't want people to have a headache when reading WP, but that is flat out wrong and the space-time view is very widely accepted. Lipsquid (talk) 19:35, 10 October 2015 (UTC)

The lead section explains the whole thing where the most accurate description of gravity is in terms of spacetime curvature but it is often still treated as a force; then the article goes on to repeatedly talk about it in terms of a force at several points, with that understanding in mind. I don't see the problem here, the lead section already solves the headache. LjL (talk) 20:01, 10 October 2015 (UTC)
lol, Gravity isn't an attractive force and there isn't any attraction between the Earth and my feet regardless of how much easier that is to understand for some people. I will fix the sentence. Lipsquid (talk) 20:06, 10 October 2015 (UTC)
I agree with LjL. Numerous physics texts describe gravity as a "force". The article explains gravity in terms of curvature, there is no need to eliminate references to "force". Rewriting this article with tortured syntax to eliminate the word "force" is excessively fussy and will make it confusing for general readers. --ChetvornoTALK 20:34, 10 October 2015 (UTC)
If you want to be "politically correct", quantum mechanics says there is no such thing as "force" in any area of physics. When you hit a nail with a hammer, the hammer is not exerting force on the nail; what is really happening is the atoms of the hammer and nail are exchanging virtual photons. Hey Lipsquid, shall we go on a mission to correct this horrible unscientific 'error' by removing the word "force" from all the articles on Wikipedia? --ChetvornoTALK 20:34, 10 October 2015 (UTC)
I understand it is tilting at windmills, but it is untrue unless they find gravitons. Lipsquid (talk) 21:40, 10 October 2015 (UTC)
I noticed an interesting scientific phenomenon when I stepped on the bathroom scales this morning. The surface of the scales forced my body to accelerate (move in a nongeodesic path) due to the curved spacetime geometry surrounding the Earth. When accelerated, the inertia of my body thus caused a deflection of the surface of the scales which was transmitted through the gears to the little needle on top. I think they've got the explanation of this effect wrong over on bathroom scale, Lipsquid. Better check it out.
I knocked my coffee cup off the desk with my elbow. Of course it just moved in a geodesic path. But because the floor of my apartment was not moving in a geodesic path because of the curved geometry surrounding the Earth, it crashed into my coffee cup, and now there's coffee all over the floor. My wife got very angry when I explained it to her in this scientifically correct way, lipsquid. I wonder why? --ChetvornoTALK 17:37, 11 October 2015 (UTC)
Maybe it was just transitory "virtual photons". Not understanding a topic is supposed to make people happy or at least that is how the saying goes. Lipsquid (talk) 18:23, 11 October 2015 (UTC)
Chetvorno Come back a year later and all the -attractive force- idiocy is gone, now I have spilled my coffee laughing. He who laughs last, laughs loudest. :) Cheers! Lipsquid (talk) 17:13, 29 September 2016 (UTC)

What is gravity? Why does it exist?

The article doesn't tell me, a layman, what gravity is and why it exists. How does one body gravitationally attract another? Is this even known? Is there a consensus on it? Or is it still a mystery of physics? deisenbe (talk) 11:53, 11 October 2015 (UTC)

Physics doesn't answer "why" things are what they are, except in terms of other physics, if known. Gravity is pretty much a basic building block of physics right now (although no, it's not really "known" - we haven't seen gravitons for example) and there is no way to explain "why" it exists short of leaving physics and getting into philosophy or theology. LjL (talk) 12:28, 11 October 2015 (UTC)
"Gravity is the resistance of bodies to the curvature of space-time and it's displayed as acceleration (causal definition)." by Chromodynamic. That is a good technical description of what gravity is. Space pushes you toward the Earth, the Earth does not pull you down. LjL is right, the "why" is not really a question for science, more philosophy or religion. Lipsquid (talk) 19:26, 11 October 2015 (UTC)

Semi-protected edit request on 7 November 2015

The equivalence principle is not correct for a charge in a gravitational field does not radiate while an accellerated charge in a non-inertial system does. This was written in the book The Quantum Theory of Gravitation (2003) by Vasily Yanchilin. He also argues that rest mass is not constant like the general theory of relativity maintains, because a cloud of particles will compress due to mutual attraction and then velocities increase. If the rest masses would remain constant then the inert masses become bigger and thus the inertia of the whole cloud increases. But it is impossible that the momentum of the inert mass of an isolated cloud of particles gets bigger. The russian scientist offers new theory based on the hypothesis that mass reduces the Heisenberg uncertainty: In the half of a particle nearest to an external mass there will be less quantum mechanical transitions to the farthest half than from the latter to the nearest half. Net result is movement of the particle towards the external mass. Big mistake in Einstein's general theory is that time is not connected to physical processes: Everybody agrees that near mass the unit of length shrinks and thus atoms become smaller. Which means higher frequencies of emitting electrons. Time is bound and measured to such. Another reasoning is that a photon passes mass according the principle of least action with as big steps (oscillations with low frequency) as possible and a minimum of these. That is why it curves around mass through a zone where time runs slower. The special theory of relativity stays valid if understood thus that c is the same in all directions at a certain time and a certain place because it is bound to the potential of the total mass of the universe (hypothesis), which decreases with the expansion of the universe. C becomes zero at the edge of the universe; there everything looses speed and direction, gets into a pure quantum mechanical state, called chaos by Vasily Yanchilin. Read what he thinks of negative energy! (Little bit more on www.janjitso.blogspot.com 11 september and before). So you may add to your list this fabulous theory, explained didactically very well in the book.

194.171.56.13 (talk) 19:35, 7 November 2015 (UTC)

A single book written by a scientist about his pet theory is not enough to establish sufficient WP:verifiability or WP:notability to be included in the article. The book is a WP:primary source. WP requires primary sources to be backed up by secondary sources (WP:PSTS). Is his theory mentioned in survey articles or textbooks in the field? Even if it is, there are many, many post-Einstein alternative theories of gravitation, some are listed in the article. How notable is it? How often has it been cited? The fact that an editor finds a theory interesting is not enough to include it. --ChetvornoTALK 21:07, 7 November 2015 (UTC)

Vector Sum claim is false

The force of gravity on Earth is the resultant (vector sum) of two forces:(a) The gravitational attraction in accordance with Newton's universal law of gravitation, and (b) the centrifugal force, which results from the choice of an earthbound, rotating frame of reference.

This claim is false, neither (A) nor (B) are true. Rotational vectors which might impart momenta either toward the direction of rotation, against the direction of rotation, or tangent to the direction of rotation have zero to do with the curvature of space-time from any point of reference. That is true even when Newtonian models where gravitons or gravitinos are exchanged between the Earth and every other object in the light cone of the expansion phase of the Universe are used to describe gravitational collapse.

Claim (A) supposes Newtonian attraction models employing gravitons and/or gravitinos being exchanged among hadrons, a model which has been replaced by Einstein's confirmed curvature model. Claim (B) is flat out wrong.

A body that is being flung away from a gravity well through centrifugal vectors is not being acted upon by any "force," but also the curvature of space-time is not being affected by the rotation of the object causing the gravity well -- outside of frame dragging, obviously, and other non-classical effects.

The effect we call "gravity" on Earth is the result solely of the curvature of space-time, and even if the Equator were rotating just below local escape velocity and Alice where to jump in to the air and impart enough momenta to be flung in to space, the accumulative momenta of the centrifugal effects and Alice's leap have zip all to do with the curvature of the well the Earth sits in as a result of the curvature of space time. The shape and density of the gravitational bending of space-time is not altered by the rotation of the Earth in any way.

I recommend that the sentence be eliminated since it's obviously not correct. Damotclese (talk) 02:05, 14 May 2016 (UTC)

This all continues to be wrong

The centripetal acceleration of the surface of the Earth varies from a maximum of 0.0339 m/s at the equator to 0 m/s2 at the poles, and reduces the strength of effective gravity by an average of...

The text does not understand that gravitation attraction is not altered in any way by centripetal effects. The gravitational attraction is not even altered when a body is in free fall!

This article is a mess, it's talking about gravity from concepts which predate Newton. Damotclese (talk) 16:52, 16 May 2016 (UTC)

It says "effective gravity", e. g. what a scale would read if you use it at the equator. --mfb (talk) 21:15, 16 May 2016 (UTC)

Article should clarify these points

When my contribution to the New Alternative Theories section, "Field Alignment theory", was rejected, I was accused of "...Every great new idea in science began with someone knowing the existing science. You clearly do not know it" Despite my having a chemical engineering education and having spent several years researching a variety of physics topics, this is undoubtedly a valid accusation. One reason why is that because I lack affiliation with any academic institution, I must pay to read articles in scientific journals. Therefore I am forced to rely on sources of information such as the Wikipedia article on gravity. As with many Wikipedia articles, the "authoritative" viewpoint is presented, but there is little that would help an ignorant person such as myself understand more deeply why this viewpoint is correct. Specifically, in the Gravity article, gravitational time dilation is mentioned. However no explanation is provided for how gravity can possibly influence time. It is obvious that gravity would have an effect on timekeeping devices such as water clocks or sand glasses, but one would expect stronger gravity to shorten, rather than dilate the time measured by such devices. Many types of devices are, or have been used as timekeeping devices; everything from the aforementioned sand and water clocks, to spring-driven watch movements, to even smoothly running engines. How can gravity possibly affect all the myriad devices used to measure time? Does gravity only affect a certain type of clock, or is "time" being used as a pseudonym for change in general? How about what was possibly the first type of clock invented by humanity - the sundial. This device depends on a steady rate of rotation of the earth relative to the sun. Does the varying gravitational force applied to the earth by other solar system bodies including the sun and planets affect the time measured by a sundial?

Another gravity-related point that I, and probably many others, are curious about is the subject of this article: http://www.theregister.co.uk/2016/05/30/earths_core_is_younger_than_its_crust/ Does this mean that due to gravitational time dilation, the earth was hollow inside for 2.5 years before it had a core? Or that the sun was hollow inside for 39,000 years? How could it mean otherwise?

Additionally I was informed that original research is not accepted. If the research is not original, does this not mean that it is in effect plagiarized? How about this article: https://www.sciencedaily.com/releases/2016/05/160518120254.htm#.V0BQLvErD_M.google_plusone_share ? This article presents the idea that according to Einsteinian relativity, the earth could be regarded as rotationally stationary, while the rest of the universe revolves around it. This is far from a new idea. According to historians, it was proposed by Ptolemy around 2000 years ago, yet the article makes no attribution to Ptolemy. What would be the Wikipedia policy on this? John David Best (talk) 02:13, 16 June 2016 (UTC)

Article talk pages are for discussions about the article, not about the subject. Everything you wrote starting with "It is obvious that gravity would have an effect..." is therefore off-topic—see wp:Talk page guidelines. I have put a formal warning about this on your user talk page. Wikipedia has no room for our own research, not in the articles, and not on the article talk pages. - DVdm (talk) 06:48, 16 June 2016 (UTC)

As a consequence? On the other hand? When does the context require those two things?

Someone reverted my edit on this page. He said that the 'as a consequence' and the 'on the other hand' that I removed were not unecessary. The literal interpretation of 'on the other hand' could suggest that there are two hands with some facts on both of them. --Turkeybutt (talk) 12:26, 4 September 2016 (UTC)

This is about [10]: one hand holds the realm of subatomic particles. The other hand holds the macroscopic scale. See oxforddictionaries.com. - DVdm (talk) 12:34, 4 September 2016 (UTC)
And when would the context require as a consequence? I believe that should only be restricted to quotations about parents punishing their kids for having bad days at school. Consequence sounds contentious. --Turkeybutt (talk) 12:47, 4 September 2016 (UTC)
Merriam-Webster. - DVdm (talk) 12:51, 4 September 2016 (UTC)
Support DVdm, his additions improve the explanation. --ChetvornoTALK 18:22, 4 September 2016 (UTC)

Nature Timeline graphic

The graphic titled {{Nature timeline}} seems to provide an incorrect link to the wiki article that refers to the History of Life timeline: https://en.wikipedia.org/wiki/Timeline_of_natural_history

rather than the more encompassing Formation of the Universe timeline: https://en.wikipedia.org/wiki/Timeline_of_the_formation_of_the_Universe

which I think is more representative of the image provided.

The History of Life timeline is simply a subset of the Formation of the Universe timeline. I was confused by the link when clearly the two images differ in scale and overall content between the linking articles. The Nature Timeline graphic and link are utilized within multiple articles. SquashEngineer (talk) 15:42, 28 September 2016 (UTC)

 Done - @SquashEngineer: Thank you for your comments - and suggestion to adjust the title-link of the {{Nature timeline}} template from "Timeline of natural history" to "Timeline of the formation of the Universe" instead - yes - agreed - template title-link has now been updated - Thanks again for your comments and suggestion - and - Enjoy! :) Drbogdan (talk) 16:03, 28 September 2016 (UTC)

New Paradigm shift for Gravity?

FWIW - Of possible interest - re a new way of understanding "Gravity"?[1][2] - worthy of mention in the main "Gravity" article? - in any case - Enjoy! :) Drbogdan (talk) 14:33, 19 November 2016 (UTC)

References

  1. ^ Padmanabhan, Thanu (November 10, 2016). "Do We really Understand the Cosmos?" (PDF). arXiv. arXiv:1611.03505v1. Retrieved November 19, 2016.
  2. ^ Staff (November 15, 2016). "Research shows paradigm shift in understanding of gravity". The Indian Express. Retrieved November 19, 2016.
The first link is identical to the second article? A cosmologist wrote another arXiv entry on gravity. I don't see the importance so far. --mfb (talk) 19:55, 19 November 2016 (UTC)

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Semi-protected edit request on 18 July 2017

2601:588:0:8A3E:6C68:17B2:C8FD:556D (talk) 19:48, 18 July 2017 (UTC)

Kids Version of The Gravitational Force. Its a very simple concept its what keeps us from floating into space. Its what keeps all objects from floating. It also brings objects closer together. Its been around longer than this earth has been. Its an amazing thing. You and I would not be here without it. We just float our way to the atmosphere. Its just that important.

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. Morphdogwhat did I do now? 20:01, 18 July 2017 (UTC)

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gravity "OR" gravitation ...

so what does "gravity center" [rigid body] and "special gravity" [i.e. mass density] mean (if it's not weight)? gravity means being grave (heavy). if we draw force vector between, it starts from weighted body (i.e. gravity) and ends to gravitator (here, earth). gravitation [: making heavy] acts on gravities, while electra and magnet make phenomena by itself: magnet makes magnetism, electra does electricity, but gravitation is "seen on" gravities. in comparison, gravitation, magnetization and electrification are in the same row.
Tabascofernandez (talk) 00:27, 24 September 2017 (UTC)

There is no "gravity center" in the article. Do you mean center of mass? --mfb (talk) 02:03, 24 September 2017 (UTC)

formula

what if we write it as kG·m·m0 /r2 where kG = 1/ 4πγ0; in harmony with kE·q·q0 /r2 {kE = 1/ 4πε0} and kM·φ·φ0 /r2 {kΜ = 1/ 4πμ0}. if that be, c2 = μ0ε0; so what does γ0 do? [s2 = γ0ζ0; kZ = 1/ 4πζ0; F = kZ·β·β0 /r2 ] (Z-field I guess it's about hydrodynamics: a moving mass object (single, or in groups: air, water ..). {compare moving charge: magnetism}. also newton law: FZ = mvK, K = β/A (compare: FM = qvB, B = φ/A, or FE = φvD, D = q/A or finally: FG = βvJ, J = m/A)
Tabascofernandez (talk) 01:26, 24 September 2017 (UTC)

The first is just rewriting constants, and everything that follows doesn't look useful at all. This discussion page is for improvements of the article, not for the discussion of personal views on the topic. --mfb (talk) 02:03, 24 September 2017 (UTC)

Representing gravity in 3D

Hi wikipedia, I have been reading lots of comments elsewhere about people not understanding the standard "trampoline" representation showing how mass creates a gravity well, it makes many think space is flat (trampoline like). Would it not be better showing a 3D representation as well or instead of? ---- — Preceding unsigned comment added by Rod Fathers (talk • contribs) 14:01, 18 October 2017 (UTC)

The trampoline visualizes two space dimensions with a 3-dimensional picture. To visualize three space dimensions we would need a 4-dimensional picture. That is not going to help people. --mfb (talk) 08:47, 19 October 2017 (UTC)
I meant something like this video clip from utube https://www.youtube.com/watch?v=hH69B0Oc2Og Rod Fathers (talk) 23:50, 30 October 2017 (UTC)
I'm not sure if that is helpful, it can be very misleading. --mfb (talk) 08:21, 31 October 2017 (UTC)
Also let's not forget that gravity is modelled/described/caused by spacetime curvature. The animations and figures only show the spatial part of the curvature. - DVdm (talk) 10:14, 31 October 2017 (UTC)

Leonard Susskind is very generic sometimes

Motion is information. The black hole limits the motion of particles, so we have jets which dissipate that relative to it's surroundings information. Gravitational systems, are constituted of objects which slowly have their particles complexity degrading. A gravitational system, forces it's components to lose information. That means that all atoms in a gravitational group, tend to have slightly closer spin values, and slightly closer time-flow pace (relative timing among particles). The information isn't lost. It's simply transformed into motion. A gravitational system is very hard to describe, because it has many components, but if we await, we then can describe with fewer pages the characteristics of the particles'except from their relative speed. Dark energy is a result of quantum fluctuations in the void. Dark energy is a cause of differentiation, thus acts in bigger orders of magnitude, as antigravity. Dark matter, is the second order gravity, among the gravitational orbits/paths and not directly the gravity of objects. Even potential paths exhibit inertia. Even particles (which are most of the time fields and not particles) are inertial flows of potentiality. The Universal void exhibits more unbiased randomness at the Planckian level than matter, but there is no void in the Universe. The Universal void is a phenomenon within our Universal topoalgebraic algorithm, thus it's not a void. — Preceding unsigned comment added by 2A02:2149:8490:3400:608A:BDA2:6DF7:A815 (talk) 11:07, 2 February 2018 (UTC)

This Talk page is not the place to present your theories of gravity; it is only for discussing the article itself, see WP:Talk page guidelines, WP:NOTFORUM --ChetvornoTALK 13:35, 2 February 2018 (UTC)

Anomalies and discrepancies

Extra energetic photons: Photons travelling through galaxy clusters should gain energy and then lose it again on the way out. The accelerating expansion of the Universe should stop the photons returning all the energy, but even taking this into account photons from the cosmic microwave background radiation gain twice as much energy as expected. This may indicate that gravity falls off faster than inverse-squared at certain distance scales.


"Travelling" really? please use spell check - traveling.


Brett TaylorRonston121 (talk) 13:57, 23 February 2018 (UTC)

Please note that on article talk pages we must discuss the article, not the subject—see wp:Talk page guidelines.
Also note that both "traveling" and "travelling" are perfect English—see [11] and [12]. And of course wp:ENGVAR and wp:RETAIN. Cheers. - DVdm (talk) 14:49, 23 February 2018 (UTC)
Known, and studied: Sachs-Wolfe effect. --mfb (talk) 00:52, 24 February 2018 (UTC)

Opening sentence needs reconsidering

Gravity or gravitation is a natural phenomenon by which all things with energy are brought toward (or gravitate toward) one another, including stars, planets, galaxies and even light and sub-atomic particles.

While the mention of "with energy" may be technically correct due to mass/energy equivalence, it is much too confusing for the ordinary reader to drop this into the opening sentence without any further (at this point) explanation. 31.49.180.255 (talk) 01:57, 26 September 2016 (UTC)

I absolutely agree. This is a good example of a common problem on WP technical articles; editors generalizing the first sentence until it is incomprehensible. There are many better ways to state this point in the intro, which a good writer would use; for example:
"Gravity or gravitation is a natural phenomenon by which all things with mass are brought toward (or gravitate toward) one another, including stars, planets, and galaxies. Since energy and mass are equivalent, all forms of energy such as light are also included."
Another dweeby example of bad writing in this introduction is:
"Gravity is responsible for many of the structures in the Universe, by creating spheres of hydrogen — where hydrogen fuses under pressure to form stars — and grouping them into galaxies"
Gravity doesn't create spheres of hydrogen out of nothing, does it? Read the sentence as if you are a non-technically-educated reader, and that's what it seems to mean. Instead, why can't we just say:
"The gravitational attraction of the original gaseous matter in the universe caused it to collapse together, forming stars — and the stars to group together into galaxies — so gravity is responsible for the large scale structures in the Universe."
This lead paragraph sounds like it was written by a teenage Sheldon Cooper, not a competent science writer. Seriously, come on. --ChetvornoTALK 03:37, 26 September 2016 (UTC)
I don't agree with the first one. Light has no mass, so suggesting that it can be "included" in "all things with mass", would be a bad idea. It can be included in "all things that gravitate or that cause and are under the influence of gravitation", but not in all things with mass. In order to avoid circularity we can't of course mention gravity or gravitation. Perhaps there is another way to state the point correctly, but I think that the the current wording is very okay. It invites the ordinary reader who might expect mass here, to be somewhat puzzled and by all means go on reading. - DVdm (talk) 08:44, 26 September 2016 (UTC)
Your proposed version would be fine with me:
"Gravity or gravitation is a natural phenomenon by which all things with mass are brought toward (or gravitate toward) one another, including stars, planets, and galaxies. Since energy and mass are equivalent, all forms of energy such as light are also under the influence of gravitation."
I don't object to a sentence that gravitation acts on "all things with energy"; I just don't think it should be the lead sentence. I just think the intro shouldn't be 'puzzling' the readers; this subject is already puzzling enough for nontechnical people. "It is particularly important for the lead section to be understandable to a broad readership." (WP:EXPLAINLEAD) "Do not hint at startling facts without describing them." (MOS:LEAD) "The average reader should not be shocked, surprised, or overwhelmingly confused by your article." (WP:ASTONISH) "[The lead] should not "tease" the reader by hinting at but not explaining important facts that will appear later in the article." (MOS:INTRO) Many general readers with no scientific education come to this page just wanting the simplest, most understandable explanation of gravity. I think the current confusing lead sentence will just discourage them. --ChetvornoTALK 21:17, 26 September 2016 (UTC)
The amended phrase "all forms of energy such as light are also under the influence of gravitation" is almost fine. I'd add something to make it complete:
"Gravity or gravitation is a natural phenomenon by which all things with mass are brought toward (or gravitate toward) one another, including stars, planets, and galaxies. Since energy and mass are equivalent, all forms of energy such as light also cause gravitation and are under the influence of it."
Do you see another acceptable way to say that these forms are also sources of gravitation? - DVdm (talk) 21:27, 26 September 2016 (UTC)

FWIW - Perhaps the following wording may be better? =>

  • Suggestion-1: "Gravity, or gravitation, is a natural force with which all things with mass are brought toward one another (including planets, stars and galaxies). Since energy and mass are equivalent, all forms of energy (including light) cause, and are influenced by, gravitation."

MORE Simply? =>

COMPARE? =>

  • Wiktionary: "Gravity, or gravitation, universal force exercised by two bodies onto each other."

IN Any case - Enjoy! :) Drbogdan (talk) 21:52, 26 September 2016 (UTC)

@Drbogdan I totally agree with Suggestion-2. "all things with mass" because everything with energy is not effected by gravity, photons for example. Whereas all things with mass are physically attracted to each other. However, light does not have its "own gravitational mass". - Worldandhistory (talk) 15:09, 28 September 2016 (UTC)
@Worldandhistory: Thank you for your comments - seems, after a casual Google Search, there may be many WP:RS that suggest photons (or light) are influenced by gravity in fact - one worthy (imo) explanation may be from the Physics Department at the University of Illinois (also see "Photon#Contributions to the mass of a system") - in any case - Thanks again for your comments - and - Enjoy! :) Drbogdan (talk) 15:29, 28 September 2016 (UTC)
@Drbogdan, if you are convinced for your proposed claim that "photons (or light) are influenced by gravity" and happen to have reliable sources to back your claim, you may add the info then. :) Best - Worldandhistory (talk) 16:11, 28 September 2016 (UTC)
@Worldandhistory: Thanks for your comments - perhaps the following quote (or at least WP:RS) may be considered in some form?

Copied from "Photon#Contributions to the mass of a system":

Since photons contribute to the stress–energy tensor, they exert a gravitational attraction on other objects, according to the theory of general relativity. Conversely, photons are themselves affected by gravity; their normally straight trajectories may be bent by warped spacetime, as in gravitational lensing, and their frequencies may be lowered by moving to a higher gravitational potential, as in the Pound–Rebka experiment. However, these effects are not specific to photons; exactly the same effects would be predicted for classical electromagnetic waves.[1]

References

  1. ^ E. g. sections 9.1 (gravitational contribution of photons) and 10.5 (influence of gravity on light) in Stephani, H.; Stewart, J. (1990). General Relativity: An Introduction to the Theory of Gravitational Field. Cambridge University Press. pp. 86 ff, 108 ff. ISBN 0-521-37941-5.
In any case - Enjoy! :) Drbogdan (talk) 16:30, 28 September 2016 (UTC)

I disagree with the suggested changes to the wording of the first sentence. I think the sentence as written accurately and succinctly establishes the more universally accepted notion that gravity is associated with energy rather than the traditionally referred to notion of mass. Even to the average reader, this article establishes correctly, right from the get-go, that to understand gravity in the present age, gravity is not a force, but rather a phenomenon, and that Newton's laws were approximations superseded by the more universal Theory of Relativity. SquashEngineer (talk) 15:42, 28 September 2016 (UTC)

Agree. Let's keep that opening sentence. It perfectly reflects the body of the article. And it is correct. - DVdm (talk) 19:51, 28 September 2016 (UTC)
@SquashEngineer Hi, can you please share a reliable source that backs your claim; "gravity is not a force, but rather a phenomenon, and that Newton's laws were approximations superseded by the more universal Theory of Relativity"? If you do please do share here for knowledge. I still think the first sentences are confusing and ambiguous. But again, I can be wrong. Best - Worldandhistory (talk) 16:11, 28 September 2016 (UTC)
Please indent the messages as outlined in wp:THREAD and wp:INDENT. Thanks.
The opening sentence reflects what is in the article and there is nothing confusing and ambiguous about it, just like there is nothing confusing and ambiguous about the opening sentence of Bing Bang, on the talk page of which you more less wrote the same as you did here. If, after having read the article, you find that something remains confusing and ambiguous, then you should probably go to the wp:Reference desk and ask topical questions there. An article talk page is not for requesting sources to support the first sentence—see WP:LEADCITE. You will find sources in the body of the article. - DVdm (talk) 19:51, 28 September 2016 (UTC)
@DVdm: I agree with you that the opening sentence is fully supported, and Drbogdan should read the sources if he has questions. But it is clear from 31.49.180.255's and Drbogdan's comments that the concept of energy gravitating is unfamiliar to many (undoubtedly most) readers and I think it needs to be explained or stated explicitly, not "sprung" on them without explanation in the lead sentence. I think your suggested wording in your 21:27, 26 September 2016 post above would be great - better than mine. I think Drbogdan's Suggestion-1 wording above would be fine, and I could live with his Suggestion-2. But not mentioning mass (or some equivalent word like "bodies" or "particles") in the lead sentence defining gravity is going to be really confusing to many. I've looked at a bunch of textbooks [13] and I don't see any that define gravity as we do. --ChetvornoTALK 22:27, 28 September 2016 (UTC)
@Chetvorno and DVdm: Thank you for your comments - to clarify - besides my own Suggestion-1 and Suggestion-2 versions of the opening lede sentence posted earlier above, the current opening lede sentence has also been *entirely* ok with me - nonetheless, I agree with the reasoning presented by User:Chetvorno - that my Suggestion-1 and/or Suggestion-2 may be preferred - and, perhaps, more reader-friendly (and accessible?) to the average reader - after all => "Readability of Wikipedia Articles" (BEST? => Score of 60/"9th grade/14yo" level)[1] (also see my related post) - in any case - hope this helps in some way - Thanks again for your comments - and - Enjoy! :) Drbogdan (talk) 23:10, 28 September 2016 (UTC)

References

  1. ^ Lucassen, Teun; Dijkstra, Roald; Schraagen, Jan Maarten (September 3, 2012). "Readability of Wikipedia". First Monday (journal). 17 (9). Retrieved September 28, 2016.
@All: ok, for now I have made the change as suggested 21:2, 26 September 2016, as indicated above by Chetvorno. Cheers. - DVdm (talk) 06:31, 29 September 2016 (UTC)

@Chetvorno, DVdm, SquashEngineer, and Worldandhistory: et al. => QUESTION: Should "Gravity", in the current opening sentence of the lede, be referred to as a "natural phenomenon" - or - as a "natural force" instead? - after all - "natural phenomenon" is wikilinked to "List of natural phenomena", which doesn't seem to currently list the term "gravity" at all (perhaps it should?) - also - the term "force" seems to be the preferred term (actually, "universal force") in "Wiktionary - Gravity", as well as the preferred term (actually, "universal force") in the "Encyclopedia Britannica - Gravity" - in any case - Enjoy! :) Drbogdan (talk) 12:19, 29 September 2016 (UTC)

Hm, I certainly wouldn't do that. After all, in general relativity, which is our best model of gravity, it is not a force at all. So it's probably better to be neutral here and leave all options open by just using the generic natural phenomenon, which is then explicitised to force and spacetime curvature later in the article, depending on the context.
But It would indeed be a good idea to include a wikilinked Gravity in that list—even if I'm not a fan of such list-articles. As far I'm concerned, go ahead with the list. - DVdm (talk) 13:49, 29 September 2016 (UTC)
 Done - @DVdm: Thank you for the comments - and suggestion to add "Gravity" in the "List of natural phenomena" article - no problem whatsoever - added "Gravity" under a newly created "Physical" subgroup - for starters at least - *entirely* ok with me to rm/rv/mv/ce the edit of course - iac - Enjoy! :) Drbogdan (talk) 14:16, 29 September 2016 (UTC)
Since it's already decided, sorry for delayed response. I agree with DVdm to be neutral here. However, according to me, it should be referred to as a "natural force", as it exists/is present with every object as can be seen here with an example of dice. The Earth's strong gravitational force simply doesn't allow two objects as small as dice to react to their gravitational forces, but if they are placed in non-gravitational environment, they will simply collide. Using the term phenomenon might not be a good idea, according to me, since there is not question or doubt about the existence of Gravity in all things. BR - Worldandhistory (talk) 17:59, 29 September 2016 (UTC)
@DVdm: the new lead looks fine to me. --ChetvornoTALK 02:09, 3 October 2016 (UTC)
@Drbogdan: Since we're making a point of being correct and not calling gravity a force in the rest of the article, it probably shouldn't be called a force in the lead sentence. --ChetvornoTALK
@Chetvorno: Thanks for your comment - yes - agreed - no problem whatsoever - Thanks again - and - Enjoy! :) Drbogdan (talk) 08:21, 3 October 2016 (UTC)
Bit late, but there really is no reason to say "everything with mass" as opposed to "everything with energy". It is simply misleading. Sir Cumference π 01:02, 5 January 2017 (UTC)
The 2nd sentence resolves any confusion. --ChetvornoTALK 02:13, 5 January 2017 (UTC)
Isn't it worth generalizing a bit more? In GR, mass isn't the only source of gravity. Energy, momentum, pressure, etc. are relevant. Perhaps we could say something more ambiguous, like "Gravity or gravitation is a natural phenomenon by which all forms of matter are brought toward (or gravitate toward) one another, including stars, planets, galaxies and even light and sub-atomic particles." Sir Cumference π 19:56, 5 January 2017 (UTC)
The 2nd sentence explains that energy is included, so I feel there is no need for the additions you propose. Other problems I have with the proposed lead:
  • The proposed sentence is logically inconsistent, since light is not a form of "matter".
  • It is also misleading since by mentioning "sub-atomic particles" explicitly it implies that gravity is a significant force on them. While of course as the constituent of all matter subatomic particles are acted on by gravity, the force of gravity on a single particle is utterly negligible. We don't want to give introductory readers the impression that gravity is a significant player in atomic physics.
--ChetvornoTALK 20:51, 5 January 2017 (UTC)

After reviewing this (exhaustive) discussion of the lead sentence(s), I would like to suggest the following change from the current "Gravity, or gravitation, is a natural phenomenon by which all things with mass are brought toward (or gravitate toward) one another, including objects ranging from electrons and atoms, to planets, stars, and galaxies. Since energy and mass are equivalent, all forms of energy (including photons and light) cause gravitation and are under the influence of it." to "Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy--including planets, stars, galaxies, and even light--are brought toward (or gravitate toward) one another." I make this suggestion in the interest of simplification and brevity.
-Catwilsonaz (talk) 20:06, 21 June 2018 (UTC)

Ok with me. - DVdm (talk) 21:23, 21 June 2018 (UTC)

Review of Sources and Citations

I have chosen to review this article's use of sources and citations in accordance with Wikipedia: Verifiability. The basis for my review is comprised of the following questions:

  • Is each fact referenced with an appropriate, reliable reference?
  • Do the links work? Is there any close paraphrasing or plagiarism in the article?

Upon my review, I have noticed many instances in which citations are needed to verify facts. I will endeavor to edit these instances to reflect that citation is needed. Existing sources seem to be reliable and appropriate with the exception of a YouTube video which no longer exists and needs to be removed. Of the sources I explored, there appeared to be no plagiarism or close paraphrasing.

- Catwilsonaz (talk) 23:01, 21 June 2018 (UTC)

Semi-protected edit request on 1 August 2018

Add an extra line above Gravitational radiation topic so it's not unaligned. Regisbsb (talk) 09:10, 1 August 2018 (UTC)

 Done: [14]. Thanks. - DVdm (talk) 09:22, 1 August 2018 (UTC)

Page Protection

Is it really required to protect a page on gravity of all things? 173.86.46.180 (talk) —Preceding undated comment added 14:55, 7 September 2018 (UTC)

Please sign all your talk page messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.
Pages aren't protected without reason. As an exercise, view the edit history and see if you can find out why it was protected. - DVdm (talk) 15:02, 7 September 2018 (UTC)
More prominent articles tend to get vandalized more, especially if it is a topic discussed in schools. --mfb (talk) 19:56, 7 September 2018 (UTC)

🌠

The whole Universe is a Feynman diagram. Empty space is virtual particles but they are connected with the standard baryonic matter. Gravity is a flow, a directional biasing towards someting; it is a direction of the birth and creation of the virtual particles. Baryonic matter is affected a. by the flow of the void, b. by losing time-flow energy, which becomes slower if the attracted object is small. — Preceding unsigned comment added by 2a02:2149:825f:3f00:15c4:2707:8443:1001 (talk) 22:49, 20 September 2018‎ (UTC)

Please see the top of this talk page: "This is the talk page for discussing improvements to the Gravity article. This is not a forum for general discussion of the article's subject." Besides: Stringing together random buzzwords doesn't produce anything useful. --mfb (talk) 23:43, 20 September 2018 (UTC)

Heavy

Who coined the term “gravity”?

What term did Aristotle, Galileo (and others) use? Any Greeks before Aristotle write about gravity? Babylonians? Persians?

NB: (I reckon) a fair bit of archives could be in the article.

MBG02 (talk) 10:01, 7 November 2018 (UTC)

Semi-protected edit request on 16 December 2018

Change "Moon's gravity causes ocean tides" to Moon's gravitational tug causes an increase in the amplitude of the ocean's tides. SithLord8 (talk) 16:57, 16 December 2018 (UTC)

 Not done: the phrase "Moon's gravity causes ocean tides" does not appear in the article. - DVdm (talk) 17:19, 16 December 2018 (UTC)

Transitional state (physics)(s); the wavefunctional time-period a collapse lasts (which isn't the same for all observers, and that is one out of the many components of the phenomenon/processes of gravitation/gravity

Quantum mechanics is mostly (but not only) the field of study of states.
Gravity is mostly (but not only) the field of study of transitional states or semistates (make page).

example: most remote control buttons have only one permanent state (they might cotrol many states of a machine due to an algorithm, usually a physical algorithm); but the remote control buttons have transitional states 1. during the period we press and 2. release the button. The electric states are more important than the mechanism of the button; but even then, one transitional state does exist; and has a duration (it isn't instantaneous). THIS IS EXTREMELY IMPORTANT! — Preceding unsigned comment added by 2a02:2149:8237:d400:4da2:87e:4fbc:47 (talk • contribs) 13:10, 5 June 2019 (UTC)

This page is for discussion of the article, not theories of gravity itself. Wikipedia is not a forum for you to present your personal theories, see WP:NOTSOAPBOX. --ChetvornoTALK 13:25, 5 June 2019 (UTC)

Gravity vs distance


This curve represents gravity between objects when the distance is increasing. The force of gravity fades gradually along an inverse square. Gravity generally decreases inside a body, shown here assuming constant density, where the curve drops off at a sharp angle. For comparison, including an actual density profile, see Earth gravity.

@Mfb: doesn't like my model gravity graphs, calling it nonsense and vandalism because it shows a constant gravity density inside a planet. Tom Ruen (talk) 14:17, 22 February 2019 (UTC)

It doesn't show a constant gravity, it shows the gravity you would get with a constant density. As the actual distribution shows this is not a good approximation at all. If you go down into Earth the gravitational acceleration is actually increasing until you reach the core. --mfb (talk) 15:31, 22 February 2019 (UTC)
Sorry, I meant "constant density". Tom Ruen (talk) 22:10, 23 February 2019 (UTC)
Actually as you go down into the Earth the acceleration of gravity decreases to zero at the center because, by Gauss's law, at a subsurface point the gravitational force does not include the gravity of the spherical shell of matter outside that radius. The further you go down, the smaller the sphere of matter inside the radius, so the less the gravitational force. In a constant density planet the mass of the sphere of matter is proportional to R3 but the inverse square force adds a factor of R-2, so below the surface the force, and acceleration of gravity, is proportional to R3/R2 or R, and thus decreases linearly with radius, as the graph shows. --ChetvornoTALK 17:51, 22 February 2019 (UTC)
@Chetvorno: As you can see from the correct graph you are wrong. In a constant density planet you would be right but there is no such thing. The image shows real objects, so it should have real data (or omit the wrong part). --mfb (talk) 18:11, 23 February 2019 (UTC)
I didn't say the Earth has constant density (it doesn't) I just said the graph was correct for a constant-density planet. --ChetvornoTALK 19:14, 23 February 2019 (UTC)
You said "The further you go down [...] the less the gravitational force" which is false for a large part of the interior of Earth, for example. It is true in a hypothetical scenario that has little in common with our world. --mfb (talk) 19:58, 23 February 2019 (UTC)
Instead of including the complication of gravity below the surface, why don't we just erase the straight parts of the graph and show the inverse square parts? --ChetvornoTALK 17:51, 22 February 2019 (UTC)
Yes: removing the straight lines would make a lot of sense. Start gravity upwards from surface. — JFG talk 23:34, 22 February 2019 (UTC)
I agree with Chetvorno: Remove straight parts, keep inverse square parts. The gravity inside the planet is for the most part irrelevant. While theoretically correct in the case of a planet with constant density, and thus not "nonsense", the diagram is not particularly useful because those planets don't actually have constant density (and thus the field inside the planet does not drop linearly). If you find a reliable source showing a diagram of the gravitational fields inside those planets, it may be a worthy addition. Until then, no. Renerpho (talk) 01:00, 23 February 2019 (UTC)

I'm fine with the outside inverse square parts. --mfb (talk) 18:11, 23 February 2019 (UTC)

There are more correct graphs available, like the second one shown here. --Geek3 (talk) 11:28, 22 July 2019 (UTC)
Gravitational field inside the earth.

Wrong Definition and meanings of Gravity

The entire wikipedia article and scientific community are completely wrong.

The Electromagnetic Radio Frequency Current or The Centrifugal Magnetic Spin Momentum or a particles magnetic spin momentum is gravity.

Like

Whirlpools in water Tornadoes Eye of the tornadoes Hurricanes Eye of the Hurricanes Typhoons Throwing bits of paper in the wake of a speeding train

This is the principle of gravity

There is no attractive force or graviton or any gravitational particle.

Spin Drag is Gravity. — Preceding unsigned comment added by AbhijeetMD (talk • contribs) 15:55, 13 August 2019 (UTC)

Please sign all your talk page messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.
All content in Wikipedia must be properly sourced—see wp:verifiability. And article talk pages are for discussions about the article, not about their subject, unless when based on wp:reliable sources, not on our own wp:original research. See wp:Talk page guidelines. - DVdm (talk) 16:16, 13 August 2019 (UTC)
"The entire wikipedia article and scientific community are completely wrong" Congratulations on your future Nobel Prize.... -Jordgette [talk] 17:13, 13 August 2019 (UTC)
Jordgette, see User_talk:Winged_Blades_of_Godric#Gravity. ∯WBGconverse 19:25, 13 August 2019 (UTC)
Lol. Novel Prize. 🤣 Masum Reza📞 21:10, 13 August 2019 (UTC)

That user has been blocked indefinitely in the meantime. --mfb (talk) 01:02, 14 August 2019 (UTC)

Misspelling of gurutvākarṣan

How do you edit this article?

The word gurutvākarṣaṇ has been misspelled as "gruhtvaakarshan". — Preceding unsigned comment added by 2602:306:c4ce:a169:2d46:788f:6f69:a4bf (talk) 04:24, 13 September 2019 (UTC)

Only registered users can edit the article. The book cited in the article writes "gruhtvaakarshan". Do you have a good reference that this spelling is wrong (and not just an alternative transliteration)? Please sign talk page contributions to make clear who wrote what. --mfb (talk) 06:58, 13 September 2019 (UTC)

It's not a matter of alternate transliteration. Even by the convention that "gruhtvaakarshan" seems to follow, the proper spelling would be 'gurutvaakarshan'. The point is that a 'u' has been dropped and an 'h' added. The word is a Sanskrit compound, gurutvā-karṣaṇam, meaning roughly "pulling by weight". You can confirm with any good Hindi or Sanskrit lexicon the meaning of the two elements, if not the complete compound. In fact I just checked Google translate and even IT, selecting for Hindi, returns "gravity" for 'gurutvākarṣaṇ'. (Copy and paste गुरुत्वाकर्षण if you try Google's translator.)

It stuck out immediately when I read the article, because Sanskrit doesn't allow the consonant cluster 'ht'. — Preceding unsigned comment added by 2602:306:C4CE:A169:C03B:FA2A:1DAC:3A9A (talk) 18:21, 13 September 2019 (UTC)

"gurutvaakarshan" has way more Google hits than the other options, and it looks like a possible spelling. I went with that. --mfb (talk) 09:01, 14 September 2019 (UTC)

natural phenomenon or observed as such?

The way the first sentence is written I think it would be better to say 'observed as a natural phenomenon whereby', thus avoiding the question of whether phenomenon is an actual descriptor in physics of something that is force-like but not a force. --2607:FEA8:D5DF:F3D9:21EB:7E3E:D765:F5EE (talk) 17:20, 1 March 2020 (UTC)

It seems to me the lead sentence is already vague and awkward enough, due to our efforts to avoid the word 'force'. No need to make it more confusing. 'Phenomenon' is a adequate description. --ChetvornoTALK 18:27, 1 March 2020 (UTC)

General Rewrite Suggestions for Accuracy, Brevity, and Clarity

Greetings fellow Wikipedians,

As a member of Wikipedia: WikiProject Science and a student editor with Wiki Education Foundation, I have chosen to focus on reviewing and improving this article. When reviewing articles, my guiding objectives are to improve the "ABCs" of the article accuracy, brevity, and clarity. In this interest, the following suggestions are put forth:

1. "On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing, forming stars – and for the stars to group together into galaxies – so gravity is responsible for many of the large scale structures in the Universe." (Introduction)
Proposed: "Earth's gravity gives weight to physical objects and the Moon's gravity causes the ocean tides. Gravity is also responsible for many of the large scale structures in the Universe because it causes gaseous matter to coalesce into stars which then form solar systems and galaxies according to their gravity."
Reasoning: Improves clarity and brevity of content.
2. Section 1.1 title: "Scientific Revolution" (Section 1.1)
Proposed: Section 1.1 title "Galileo"
Reasoning: All content in this section has to do directly with Galileo. The overall theme of the section is Galileo, not the Scientific Revolution.
3. "Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries." (Section 1.1)
Proposed: "Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries during the period known as the Scientific Revolution."
Reasoning: If suggestion 2 is followed, this would improve the accuracy of this section.
4. "Newton's theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets." (Section 1.2)
Proposed: "Newton's theory was used to predict the existence of Neptune based on observed motions of Uranus that could not be accounted for by the actions of the other planets."
Reasoning: Opinions such as "greatest success" should be avoided when stating facts.
5. "The application of Newton's law of gravity has enabled the acquisition of much of the detailed information we have about the planets in the Solar System, the mass of the Sun, and details of quasars; even the existence of dark matter is inferred using Newton's law of gravity." (Section 2.3)
Proposed: "Our knowledge of gravity has led to scientific breakthroughs concerning our Sun and planets in our Solar System, quasars, and even dark matter."
Reasoning: Improves brevity and accuracy by removing unsupported content. I challenge that these breakthroughs are the result of Newton's law of gravity specifically, and pose that these breakthroughs are more result of our general understanding of gravity including both Newtonian and Einsteinian contributions.
6. "In February 2016, the Advanced LIGO team announced that they had detected gravitational waves from a black hole collision. On 14 September 2015, LIGO registered gravitational waves for the first time, as a result of the collision of two black holes 1.3 billion light-years from Earth." (Section 2.4)
Proposed: "In February 2016, the Advanced LIGO team announced that they had detected gravitational waves for the first time on 14 September 2015 as a result of the collision of two black holes 1.3 billion light-years from Earth.
Reasoning: Improves brevity.

- Catwilsonaz (talk)

Above comment made 21 June 2018. Schazjmd (talk) 17:10, 9 August 2020 (UTC)

Addition of "Einstein-Cartan Theory" to the list of active (not historical) theories in the Wikipedia article "Gravity"

The use of "force" is per Einstein-Cartan Theory, endorsed by Einstein thru written conversations with Cartan, about 14 years after Einstein's publication of General Relativity, and well before his loss to Bohr in the EPR Paradox discussions of the mid-1930's. ECT accomodates the concept of particulate spin (discovered in the mid-1920's), and can reportedly be derived from GR, per the latest (Version 26) Arxiv preprint of an article by Petti. It is widely reported to be more sophisticated (mathematically) than GR, and has allowed elimination of the cosmological "singularity", as described by Nikodem J. Poplawski in numerous papers preprinted on Arxiv between 2010 and 2020, several of which were subsequently published. The addition of Einstein-Cartan Theory to the list of active (not historical) "theories of gravity" is essential to the plausibility of the Wikipedia article "Gravity", and its current absence from that list renders the entire article questionable. [Here's a link to the final version--Version 26--of Petti's preprints of "Derivation of Einstein Cartan theory from general relativity": https://arxiv.org/abs/1301.1588 . I apologize for having described it as the derivation of GR from ECT in the earlier discussion, but I'm mainly concerned with getting ECT into the list of active theories, with both Petti's preprint and at least one by Poplawski having appeared earlier in 2020.]Ole Berson (talk) 17:28, 11 August 2020 (UTC)

Potential external link

Could [15] be an appropriate external link? The author has a PhD in physics education and the video is a pretty good exposition of the difference between general relativity and Newtonian conceptions of gravity. Ovinus (talk) 02:03, 10 October 2020 (UTC)

Earman, John; Glymour, Clark (1980)

New critics about Earman, John; Glymour, Clark (1980) critics:

https://royalsocietypublishing.org/doi/full/10.1098/rsnr.2020.0040?af=R

--Luxaba (talk) 12:00, 28 October 2020 (UTC)

Making the lead section layman-accessible

Under the guidance of Wikipedia:Make technical articles understandable and MOS:INTRO ("Provide an accessible overview"), I recently edited the lead section to begin as follows:

Gravity or gravitation (from Latin gravitas 'weight') is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another. Gravity is a physical connection between space and matter that is precisely described by Einstein’s geometric theory of gravity. In simple terms, the theory states that matter curves the space around it, and it moves with respect to the curvature of space, including curvature caused by other matter. ...

I believe this is a broad and accessible overview of what gravity is, how it affects the universe, and how it's understood by physicists. However, over the course of a number of revisions, my work in accomplishing this was almost entirely undone. Compare to the opening paragraph of the current revision:

Gravity (from Latin gravis 'heavy') is a physical connection between space and matter that is precisely described by Einstein's 1915 geometric theory of gravity known as general relativity. Put simply, that theory says, "Space acts on matter, telling it how to move. In turn, matter reacts back on space, telling it how to curve." Here and below, the word space is equivalent to spacetime. ...

I believe that the current version of the article's lead section is too technical for a layman to understand or glean any useful knowledge from. (I've only quoted the first paragraph here, it being the most important, but my concern relates to the whole lead section.)

Some of the edits seem to push for a distinction to be made between "gravity" and "gravitation", but this distinction is absent from the lead section. To a layman, these terms are fully synonymous; gravity is gravitation. So if the article is to make a distinction, one would expect to find in the lead section an explanation of both terms and the difference between them, along with a note that the distinction is not common in casual speech.

I was also baffled by an edit summary that described the last sentence in my version of the quoted paragraph as "an poor interpretation" of the quote "Space acts on matter ...", which my version paraphrased; the original quote was reinstated in place of my paraphrase because the paraphrase "ignores the subtle philosophical difference". The current revision of the article provides no context and does not attempt to explain what that "philosophical difference" might be, so I don't know how other readers could be expected to understand it any better than I did. (Speaking of quotations, the article had too many quotes before my edit, and it once again has too many now. I feel that they're only serving to hinder the accessibility; most or all of them can and should be paraphrased.)

Because the edits have effectively reverted my contribution, I want to know what other editors think. Is the current version of the lead section really of any use for a layman? — Ardub23 (talk) 05:22, 3 November 2020 (UTC)

I agree`with virtually all of Ardub23's criticisms and have a few more. The definition of Newton's law of gravitation, "...a force causing any two bodies to be attracted toward each other, with magnitude proportional to the product of their masses and inversely proportional to the square of the distance between them", the most widely used definition, has been removed and replaced by a metaphorical quote by Newton that misleadingly defines gravity as centripetal force. This is sure to confuse general readers. Also the practical examples of gravitation: the Moon and tides, weight and formation of planets and galaxies, and the classification of gravity as one of the four fundamental forces have been removed. I think all of these items have to be in the introduction. The stuff about the geometry of spacetime can be relegated to the body of the article. I don't think a distinction between the words "gravity" and "gravitation" is supported by a majority of sources. Also the introduction is supposed to be no more than 4 paragraphs.
I'm sorry but I think all of Darylprasad's edits should be reverted, back to perhaps the 06:15, 10 October 2020‎ version. I'm okay with Ardub23's version of the lead paragraph above.--ChetvornoTALK 06:56, 3 November 2020 (UTC)
  • Another article where random churn over the years has caused a serious deterioration in understandability/readability of the lead section. People come along trying to "do good", and basically just f*ck up what was already OK. 2A00:23C8:7B08:6A00:6450:3519:2A88:94C2 (talk) 23:51, 6 November 2020 (UTC)

Fair enough. Thank-you for taking the time and effort to explain your actions...Regards Daryl. PS: I think Google liked my introduction because they had it ranked number 1 on top of NASA's. I see the current introduction is not as well favoured by Google and the article ranks at number 3...as it should be. Darylprasad (talk) 11:36, 11 November 2020 (UTC))

@Darylprasad: I think a lot of your content was good and could be added to the article body. It's just that there will be elementary-school students, HS dropouts, English majors, and overworked single mothers trying to get through community college coming to this article. They may not be able to understand your introduction; they may be looking for the simplest possible explanation of gravity. These are arguably the people who most need Wikipedia. Most of the article will be beyond them, but we should try to make the introduction comprehensible to as wide a range of readers as possible (WP:EXPLAINLEAD, WP:UPFRONT). --ChetvornoTALK 19:29, 19 November 2020 (UTC)

Semi-protected edit request on 11 December 2020

I think we should also add gravity as part of a series on General Relativity. 2405:201:600B:C84A:782F:D93E:EC23:F5D1 (talk) 12:23, 11 December 2020 (UTC)

 Already done. See Gravity#General relativity. ◢  Ganbaruby!  (Say hi!) 12:35, 11 December 2020 (UTC)

Semi-protected edit request on 23 May 2021

Change the link light (in the lead) to electromagnetic radiation (as it does not just refer to visible light). Preferably use a WP:PIPED link ([[electromagnetic radiation|light]]).108.46.173.109 (talk) 01:23, 24 May 2021 (UTC)

Done. --mfb (talk) 10:51, 24 May 2021 (UTC)

Fundamental force

  1. Gravity is fundamental, not a consequence of anything else

I'm no expert on Wikipedia or physics but isn't this wrong or at best misleading: "describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass." Gravity is not a consequence of anything. It is one of the four fundamental interactions known to physics, meaning it is not (so far as we now know) reducible to anything else. Gravity is our description of the attraction between masses, and curved spacetime is at best a consequence of that attraction. A further point related somehow to that: Does gravity curve spacetime or make masses move along the geodesic lines of curved spacetime mentioned here? No, not if spacetime is only another of our descriptions of something, a construct of the imagination by which we attempt to understand the movement of masses. If I'm sketching a face and erase a line and redraw it more accurately, has that face changed my sketch? No, and can gravity curve spacetime in any other sense? In any case Einstein made gravity more fundamental, not less, and made space and time less fundamental, more contingent than Newton had. In short: gravity may have many consequences and effects, but is never itself a consequence or effect. This line might better say, for example: "describes gravity as the fundamental attraction between masses by which masses seem to move along the geodesic lines of a curved spacetime." Oop, need to sign this, don't I? John Hicks, logged on as JohnOnlineHicks, or John Hicks (talk) 16:12, 20 May 2021 (UTC) if that tells something more.

But modern physics doesn't describe gravity as a fundamental attraction. It describes the apparent attraction between masses as a consequence of spacetime curvature. I think the fundamental/irreducible aspect is that mass–energy and spacetime curvature are linked, although we don't know the mechanism of this linkage, whether it is directly causal, etc. I've heard a lot of people say that "gravity curves spacetime" but it's more like the other way around. Saying that gravity curves spacetime is a bit like saying that darkness extinguishes photons. -Jordgette [talk] 18:06, 20 May 2021 (UTC)

Hi Jordgette: If you're right then the Wikipedia article on fundamental interactions is wrong: "There are four fundamental interactions known to exist:[1] the gravitational and electromagnetic interactions, which produce significant long-range forces whose effects can be seen directly in everyday life, and the strong and weak interactions, which produce forces at minuscule, subatomic distances and govern nuclear interactions." As I understand this, the attraction between masses is fundamental, not a side effect of something else. A separate question: What do we mean when we say that attraction between masses ("gravity") curves spacetime, not the other way around? Does our own loose talk deceive us if we say gravity curves the path by which light travels? Gravity bends the light, not some path. Observing this and attempting to predict it, we construct a path. There are no paths among the stars. In short: the attraction (or interaction) between masses is fundamental and cannot (so far) be further reduced to a side-effect of something else, including in this case spacetime, whatever that may be. Right? — Preceding unsigned comment added by JohnOnlineHicks (talk • contribs)

If you continue on to the second paragraph at Fundamental interaction, you will find: "The gravitational force is attributed to the curvature of spacetime". There is no contradiction between the two articles. That an interaction is fundamental does not mean that it can't be attributed to (or caused by) something else. It is not an issue for gravity to be a consequence of curved spacetime, just as it is not an issue that the strong force is a consequence of interactions with gluons. - MrOllie (talk) 23:36, 20 May 2021 (UTC)
Thank you, MrOllie, but I'm still not clear on this. If "fundamental does not mean that it can't be attributed to (or caused by) something else" then what meaning is left for it? As the article Fundamental interaction defines it, "In physics, the fundamental interactions, also known as fundamental forces, are the interactions that do not appear to be reducible to more basic interactions." Said another way, they cannot by explained as effects of other causes, wouldn't you agree? Then in some loose sense we can say that gravity bends spacetime but not the other way around, not even loosely, and this much we can know without deciding what to make of spacetime? John Hicks (talk) 01:35, 21 May 2021 (UTC)
Hi John, I'll add by elaborating on a couple of your points. Gravity bends the light, not some path - The path through curved spacetime does bend the light, as seen by observers along the path. There are no paths among the stars - There is a geometry of spacetime among the stars. Light travels straight lines (geodesics) through that geometry. Gravity just is the geometry, like how the coming-together of longitude lines as you go toward the poles just is the geometry of Earth. It's counterintuitive because time is one of the four spacetime dimensions, and we're only used to thinking of geometry as lines in three dimensions of space. -Jordgette [talk] 00:45, 21 May 2021 (UTC)
Thank you for your gluon example, MrOllie, to help clarify spacetime. These particles are at first hypothetical. Here, hypothetical explanations of the strong force, another of the four fundamentals alongside gravity. "Soon after the postulation of quarks, it was suggested that they interact via gluons, but direct experimental evidence was lacking for over a decade." The gluon was at first only a useful unit of measure in that exchange. Doesn't spacetime serve a similar purpose in our attempts to measure and predict gravitational effects? Not an explanation of them, only a method of predicting them? Much of quantum physics still struggles with the difference, and successfully predicts more than it can explain. Isn't spacetime geometry just a hypothesis we had wrong for centuries, while gravity, being fundamental, marched on with or without explanations from us?John Hicks (talk) 01:36, 21 May 2021 (UTC)

Sorry to be tiresome, but how can we leave this sentence in its current form? One way we might simplify this question, for ourselves and Wikipedia readers? Step back from the physics and look at the language here, the shape of the sentence in question and the words it uses. "...the general theory of relativity (proposed by Albert Einstein in 1915), which describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass." 1. First, terminology: Is light a consequence of electromagnetic radiation within a certain range of the electromagnetic spectrum? No, just another name for it. Just as we now know, thanks to Einstein, that gravity is just another name for the fundamental attraction between masses. Nevermind that we misused the names light and gravity for centuries. 2. Would we say light is a consequence of charged particles moving in narrow range of frequencies caused by uneven distribution of charged particles? No. Light is a synonym here, not a consequence. But haven't we said the equivalent about gravity? Made one synonym the consequence of another, with an intermediate step obscuring the mistake? 3. Our sentence has A (gravity) a consequence of B ("masses moving along geodesic lines in a curved spacetime") which is in turn caused by C (uneven distribution of mass). That makes A (gravity) highly derivative, at the end of a sequence of consequences. What causes C to lead this parade? Why do those unevenly distributed masses (C) move at all? As a consequence of what? Do they spy geodesic lines under their feet, as actors find their marks on a stage? No, masses move because they are drawn to one another for reasons we cannot (so far) trace further. That attraction is not, so far as we know, a consequence of anything else. For lack of any further explanation we call this attraction fundamental, which puts it alongside electromagnetics (including light) on a very short list of four fundamentals. Another name for this fundamental attraction? Gravity. Now the loop in our sentence surfaces and comes into view: Gravity (A), which is the attraction between C (unevenly distributed masses), causes B (their movement of some puzzling kind), which then causes A (gravity). Our sentence cannot be right in this form. A clearer form would leave less room for error. 4. Simpler still, ask yourself this: if gravity is a consequence of curved spacetime, what is curved spacetime a consequence of? What bent it? What curved it? Not the uneven distribution of masses. Such masses might have kept to their same places forever if not for some attraction between them. What attraction? Gravity, AKA the fundamentally inexplicable attraction between masses. 5. Couldn't we fix this sentence by (in a way) reversing it? Newton made space and time fundamental and made light and gravity their captives. We perpetuate a trace of Newton's error if we make gravity a consequence and curved spacetime its cause. Einstein reversed this, describing gravity as a fundamental and inexplicable attraction between masses, and the apparent curving movement of those masses (including even light) as a consequence. How about something like this? describes gravity as the fundamental and inexplicable attraction between masses by which, in the near vicinity of other masses, they seem to move along geodesic lines in a curved spacetime.John Hicks (talk) 17:49, 21 May 2021 (UTC)

No, you've got it backward. If you accept that the Einstein field equations are accurate (virtually every physicist does), this is very 'explicable.' What we perceive as an attraction in 3 dimensions is not truly an attraction at all, it is just an object moving in a straight line through a curved spacetime. There is no reason to change the article to sound like this is in doubt by adding wiggle words like 'seem to' or the flatly incorrect 'inexplicable' - MrOllie (talk) 18:20, 21 May 2021 (UTC)
John, if you can find some reliable sources agreeing with you that in context of general relativity, the attraction between masses is fundamental, then you might have something. But I really doubt you will find reliable sources saying that, so unless you can point us to some, you're wasting your time and ours. -Jordgette [talk] 19:41, 21 May 2021 (UTC)


I think this is mostly just an argument caused by differing usages of the word 'gravity'. Words are important, of course (although John Hicks wall'o'words above is WP:TLDR). In general I agree with Jordgette and MrOllie, the existing text is adequate:

  • I disagree with Jordgette that "...mass–energy and spacetime curvature are linked, although we don't know the mechanism of this linkage...". As MrOllie said they are linked through Einstein's field equations. Gravitation is as well understood as any of the other forces, and perfectly well enough to describe unambiguously in our article.
  • In Newton's theory, the term 'gravity' had a single meaning, it was a force between masses. So you could say things like "the gravity of a mass attracts other masses".
  • In GR, gravitational attraction is no longer considered a 'force', in the same sense as the Coulomb force between charges is. As Jordgette implied, masses influence each other's motion, but they do so indirectly through an intermediary, the spacetime metric. So our article avoids saying masses exert force on each other, or 'attract' each other. This gets a little awkward syntactically, so I wouldn't mind limited use of the phrases 'apparent force' or 'apparent attraction' in the intro.
  • As a result in GR the word 'gravity' has become slightly ambiguous, it covers two different processes: the curvature of spacetime by mass, and the tendency for masses to follow geodesic world lines. We should be more careful about using it. What does "gravity curves spacetime" mean? It should be replaced by the more precise: "mass (or mass-energy) curves spacetime".
  • "Gravity is one of the four fundamental interactions in physics" is supported by numerous sources and has to be in the article. It's an example of the proper use of the word. Here 'gravity' means the whole theory of gravity, the general theory of relativity.
  • The sentence "The general theory of relativity... describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass." seems good enough to me.

--ChetvornoTALK 04:30, 22 May 2021 (UTC)

Thank you all.

I hope I have not wasted yours or anyone's time, Jorgdette.

I took extra time over this because an article explaining Einstein is a good (tough) test for the Wikipedia approach. I still believe we need to clarify our explanations, but I don't have the expertise we need.

Sorry for my clumsy attempts at formatting here.

Time for me to revisit my library and see why I imagined gravity as fundamental rather than a consequence.

If my "inexplicable" goes too far, MrOllie, how about "not reducible," as the Wikipedia article on these four fundamental interactions says?

That article also calls them "fundamental forces." Better, isn't it? Interactions sounds like a cop-out, a fuzziness that allows circular reasoning to go undetected. We have not explained an interaction until we explain the forces within it, back and forth, in sequence.

Thank you, Chetvorno, for this: "masses influence each other's motion, but they do so indirectly through an intermediary, the spacetime metric." I'm eager to chew on that and see what I've missed, why I still smell a loop, and why this metric reminds me of the luminous aether Einstein blew away, a medium for the propagation of light.

Can't agree, though, with your definition of gravity as "the whole ... general theory of relativity." Says our Wikipedia article on the four fundamental interactions: "Second, gravity always attracts and never repels." Here gravity cannot mean the whole of Einstein's theory.

Is gravitation mediated?

More mysteries await us: "Merging general relativity and quantum mechanics (or quantum field theory) into a more general theory of quantum gravity is an area of active research. It is hypothesized that gravitation is mediated by a massless spin-2 particle called the graviton." Not by "an intermediary, the spacetime metric"?

Also from Wikipedia on the four fundamental interactions: "The modern (perturbative) quantum mechanical view of the fundamental forces other than gravity is that particles of matter (fermions) do not directly interact with each other." But in gravity they directly interact?

John Hicks (talk) 08:38, 23 May 2021 (UTC)

"Interaction" is preferred in particle physics as the interactions are not necessarily acting like classical forces. That's particularly important for the weak interaction. I'm not really sure what the point of the rest of your very long comment is. --mfb (talk) 09:05, 23 May 2021 (UTC)

Britannica: As the American theoretical physicist John Wheeler put it, matter tells space-time how to curve, and space-time tells matter how to move.

I was wrong in two ways and apologize. 

1. yes, spacetime mediates between masses; masses interact by deforming spacetime, not instantaneously across great distances. 2. this loop is simply an interaction, not circular reasoning

I once knew this! My example: If my tiny daughter and I plop down on a flimsy mattress to read a bedtime story, my weight makes a depression in the mattress that tumbles her into me. I have not pulled her. I have only moved her indirectly, by moving the mattress under us both.

Would the sentence I questioned be clearer this way? "...shows that gravity only appears to be a force where actually a mass moves along a geodesic line in a spacetime curved by other masses."

How reconcile this and the Wikipedia article on Fundamental Interactions? There gravity is a force, an attraction between masses ("always attracts, never repels"), much the way Newton left it.

Similarly the Britannica article on gravity talks at great length about Newton and less about Einstein: "The prime example of a field theory is Einstein’s general relativity, according to which the acceleration due to gravity is a purely geometric consequence of the properties of space-time in the neighbourhood of attracting masses." Is gravity as a force purely illusion then?

Should the two Wikipedia articles leave a middling scholar like me wondering: How then does mass deform or curve spacetime? Not by attraction, eh? And not by attraction between masses, unless spacetime has mass?

Britannica is also vague: "Space-time is a four-dimensional non-Euclidean continuum, and the curvature of the Riemannian geometry of space-time is produced by or related to the distribution of matter in the world." Produced how? Related how? Only some very advanced math can account for it.

Not saying either article is wrong, only speaking as a reader for whom their overlap could and maybe should be more clearly reconciled.

Have my comments here been useful?

John Hicks (talk) 16:27, 23 May 2021 (UTC)

Thoughtful views and feedback like yours are always important and useful for seeing how the article is deficient. I agree the article wording can probably be improved, but this is an inherently difficult, esoteric subject. I haven't seen any changes that I think are clear improvements yet:
  • The term "fundamental force" is a widely used traditional term and we're kind of stuck with it. Gravity along with the other 3 forces is considered "fundamental" not because it is simple but because it is not due to more basic forces. "Force" is a good descriptive term because all 4 act as forces, but physicists prefer "fundamental interaction" because each is more complicated than a simple "force", altho it is difficult to explain how. The 3 other forces: strong, weak, and electromagnetic, are actually quantum fields; at the tiny quantum level there is no such thing as a "force" and they act by exchanging particles carrying momentum.
  • For example, a magnet lifting a piece of iron is an example of the electromagnetic interaction. The magnet creates a magnetic field, which exerts force on the iron. But on a quantum level it can alternately be described as the atoms of the magnet and iron exchanging particles called virtual photons, which carry the force.
  • Gravity is not considered a force for a different reason, because it acts by altering the geometry of spacetime. Your analogy of your sagging mattress creating an apparent force between bodies is on point. The article tries to illustrate this with the widely-used diagram of a planet creating a depression in a rubber sheet that is meant to be spacetime [16]. I like your Wheeler quote: "Matter tells space-time how to curve, and space-time tells matter how to move"; I think that could be in the article.
  • I'm not sure what you mean by: "Second, gravity always attracts and never repels. Here gravity cannot mean the whole of Einstein's theory." Einstein's general theory of relativity is the accepted standard theory of gravity. It duplicates all results of Newton's theory to high accuracy. As far as I know (unless we are talking about exotic modifications like the cosmological constant) the general theory of relativity always results in attractive "forces" between masses, not repulsive ones.
--ChetvornoTALK 21:26, 23 May 2021 (UTC)
Thank you, Chetvorno. "Gravity always attracts and never repels." A quote from Wikipedia, Fundamental Interactions. You're right, my comment could have been clearer: "In this sentence, used this way, gravity cannot mean the whole of Einstein's theory." John Hicks (talk) 11:53, 1 June 2021 (UTC)

Before we leave these questions behind:

I am not the first or only reader who comes to Wikipedia to refresh what I once studied.

What did the job for me: Britannica.

Consider the unreconciled differences between the responses to my questions here:

Jordgette was wise to say that the way mass curves spacetime is not well understood. I would be wise to quote her, not paraphrase.

MrOllie and Chetvorno cannot mean what they reply, that "they are linked through Einstein's field equations." The mechanisms of gravity worked long before Einstein or his equations.

Quantum physics carefully distinguishes what we can calculate (more) from what we can explain (less).

We don't want to confuse the two mechanisms: the mechanism we study and the mechanism by which we study it. Here, spacetime. We speak of spacetime both ways and risk a muddle. We risk making spacetime the new luminous aether, a medium for propagating all that we don't yet understand.

Britannica: "the acceleration due to gravity is a purely geometric consequence of the properties of space-time in the neighbourhood of attracting masses." Purely geometric? Merely geometric? Merely appearance? Merely illusion? Surely gravity worked just as well before any human could teach it geometry?

Chetvorno wisely recommends "apparent force" or "apparent attraction."

Maybe the problem is that word "consequence." We can mislead ourselves with it. A physical process has two kinds of consequence: physical consequences and consequences for our understanding. What was the flat earth a consequence of? Human misunderstanding. Maybe "implication" instead of "consequence" to warn that our understanding may be incomplete or wrong?

Can we clearly state what we do and do not know, each of us? "We" can mislead as well. Who is we? How many of us can speak for everyone? Not many. The surest of all answers: I'm not sure.

Grateful to you all for your responses, your expertise, and your efforts to understand and explain for us all. John Hicks (talk) 11:53, 1 June 2021 (UTC)

"At present"

@Chetvorno: The statement "Gravity is most accurately described by the general theory of relativity" gives the erroneous impression that the general theory is incapable of being replaced by something more general, tomorrow or in a thousand years, which is untrue.

I mean, suppose the year is 1800. Should we write "Gravity is most accurately described by Newton's law of universal gravitation"? Knowing what we know now, we know that is not true. Can we confidently say that 100 years from now, General Relativity will still be the most accurate description of gravity? No, we cannot.

Science is not a set of true statements, it is a set of statements that have, so far, not been proven false. I think you see what I am driving at, and why I think this statement can be improved. Perhaps "To date, the most successful description of gravity is given by the general theory of relativity". If you have a better idea, please implement it. Regardless, I will not edit this article again on this point unless we have agreement. PAR (talk) 19:45, 26 May 2021 (UTC)

By that logic we should add 'At present' in front of any scientific statement in the encyclopedia. - MrOllie (talk) 20:25, 26 May 2021 (UTC)
Agree with MrOllie, this is inconsistent with the rest of WP scientific articles, and misleading for general readers. It is understood that science is an ongoing discipline and scientific theories may be replaced by better ones in the future. We don't preface every WP article on a scientific theory with "at present". So the implication of inserting it here is that there is some other gravity theory which is about to replace general relativity in the near future. Although there is plenty of research on quantum gravity theories, none are anywhere near ready to replace GR. --ChetvornoTALK 21:04, 26 May 2021 (UTC)
Agree with MrOllie and Chetvorno too. Gravity is indeed most accurately described by the general theory of relativity, and more accurately than by Newton's theory, which, more than 100 years ago, described gravity most accurately. The latter did not imply anything about now, as the former does not imply anything about the future. - DVdm (talk) 21:34, 26 May 2021 (UTC)
We don't need to put "at present" in front of every scientific statement and article, only the ones that phrase it in a way that suggests that a final truth has been found. The whole paragraph is sort of a historical account of Newton's theory being superceded by Einstein's theory, which is more general and accurate. What about something like:
Newton's law of universal gravitation was the first scientific description of gravity, which described gravity as a force causing any two bodies to be attracted toward each other, with magnitude proportional to the product of their masses and inversely proportional to the square of the distance between them. The general theory of relativity (proposed by Albert Einstein in 1915), is a more accurate and general theory of gravitation, which is essentially equivalent to Newton's law for non-relativistic situations. General relativity describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass. The most extreme example of this curvature of spacetime is a black hole, from which nothing—not even light—can escape once past the black hole's event horizon.
Note that no "at present" statement is needed. Everyone seems to at least understand my objection, so I will leave it at that. PAR (talk) 09:35, 27 May 2021 (UTC)
Your sentence: "The general theory of relativity (proposed by Albert Einstein in 1915), is a more accurate and general theory of gravitation..." falsely implies that there are other equally accurate theories of gravitation. --ChetvornoTALK 15:08, 27 May 2021 (UTC)
No, I cannot agree - "Saturn is larger than Mars" does not imply that there are other equally sized planets. It simply means that Saturn is larger than Mars. It does not imply that Saturn is the largest planet. Maybe it is, maybe it isn't. The above statement concerning gravitational theories simply means what it says. Can you say with confidence that the general theory of relativity will never be subsumed by a more accurate and general theory? No, you cannot. To say that general theory is the most accurate description of gravity leaves the reader hanging. The most accurate possible? The most accurate so far? The most accurate known? All I'm saying is let's be clear. PAR (talk) 02:06, 28 May 2021 (UTC)
On second thought, I sort of see your point. It doesn't imply other equally valid theories, but it leaves that question open. How about "Newton's law of gravitation has been superseded by the general theory of relativity (proposed by Albert Einstein in 1915), which is a more accurate and general theory of gravitation, and is essentially equivalent to Newton's law for non-relativistic situations.PAR (talk) 03:23, 28 May 2021 (UTC)
No, the correct analogy would be if our article on the planet Jupiter were to say "Jupiter is one of the largest planets in the Solar System" instead of "the largest". --ChetvornoTALK 05:29, 28 May 2021 (UTC)
Do you think the above restatement corrects the problem?
While I doubt a solar planet larger than Jupiter will be found, I have little doubt that a more accurate and comprehensive theory of gravity will be found, maybe a hundred years from now, maybe a thousand. Any suggestion that the general theory of relativity is the final word on gravity should be avoided. I think the above restatement reflects the present supremacy of the general theory without implying that it is the final truth. PAR (talk) 18:07, 28 May 2021 (UTC)
I agree with Chetvorno, we should not be trying to 'future proof' the article against possible revolutions in science. Also The "essentially equivalent to Newton's law for non-relativistic situations" isn't great. Newton's law gets the orbit of Mercury wrong, for example, and that isn't a relativistic situation. The article's current "for most applications, gravity is well approximated by Newton's law" doesn't have this problem. - MrOllie (talk) 18:19, 28 May 2021 (UTC)
The precession of the orbit of Mercury is most certainly a relativistic effect, basically because gravity propagates at the speed of light, rather than instantaneously as in Newton's theory: To quote from the Wikipedia article Tests of general relativity:

In general relativity, this remaining precession, or change of orientation of the orbital ellipse within its orbital plane, is explained by gravitation being mediated by the curvature of spacetime. Einstein showed that general relativity agrees closely with the observed amount of perihelion shift. This was a powerful factor motivating the adoption of general relativity.

Also, why should we not 'future proof' the article against possible revolutions in science? Science is not future-proof, why pretend that it is? PAR (talk) 02:49, 29 May 2021 (UTC)
PAR (talk · contribs)

Doing that everywhere is too awkward. "As of May 2021, Paris is the capital of France". Sure, it might change. But (a) it's not likely to happen anytime soon and (b) it's guaranteed that the article will be adjusted if it changes. Wikipedia always reflects the current knowledge, it can't do more than that. 90% of Mercury's perihelion precession can be explained in Newtonian physics as influence of other planets, by the way. --mfb (talk) 06:45, 29 May 2021 (UTC)

You're right, I should have said "anomalous precession" rather than precession. The Wikipedia article correctly refers to the "remaining precession". But I am not advocating that every article be overhauled, that's crazy. All I am saying is that when we are talking about a theory's place in the scientific body of knowledge, or the comparison of two apparently conflicting theories, only then do we have to be careful. And it need not be awkward. The statement "the most accurate description of gravity..." is speaking to the theory's place in the body of science, and there we have to be careful. In an article on Newton's theory alone, no changes need be made. On an article on general relativity, no changes need be made. But in an article on gravity where we are comparing the two, or addressing their validity, then I'm hoping for some accuracy.
If the people of France vote to change the capital, it changes, but if they vote to repeal the law of gravity, they are out of luck. "Paris is the capital of France" is outside the realm of science, and I'm only talking about science.
@@PAR:: Your above restatement has exactly the same problem. Also agree with MrOllie that "essentially equivalent to Newton's law for nonrelativistic situations" isn't great. --ChetvornoTALK 18:55, 28 May 2021 (UTC)
To say "for most applications, gravity is well approximated by Newton's law" is too parochial. For a communications engineer working with satellites and GPS systems for your IPhone, none of the applications use Newtonian gravity. For an engineer involved with high precision atomic clocks, none of the applications use Newtonian gravity. Newtonian gravity is used for calculating space probe trajectories, but without those atomic clocks, the calculations would be useless. For most everyday applications, we use an approximation to Newtonian gravity developed by Galileo - We say the acceleration due to gravity is constant, so the weight of an object is simply proportional to its mass, which works since our distance from the center of the earth is essentially constant. "general relativity is essentially equivalent to Newton's law for non-relativistic situations" has none of these problems. PAR (talk) 02:49, 29 May 2021 (UTC)
Very few people work with satellites or the details of GPS. For almost everyone Newton's law is an excellent approximation for everything they do, the statement you quoted is correct and easier to understand than your proposal. Constant acceleration is another good approximation in many cases, but not as many as Newton's law. --mfb (talk) 06:45, 29 May 2021 (UTC)
When you go into a grocery store and read "net weight 2 pounds" or "net weight 12 ounces", do you think "well that's fine for people at sea level, but what about me, sitting here at 1000 feet above sea level?" When some guy brags about pressing 300 pounds in Denver, does anyone remind him of the fact that it was actually slightly less, since Denver is a mile high? 99 percent of everyday people make the constant acceleration assumption 99 percent of the time whenever they draw no distinction between weight and mass. Does anyone other than people doing orbital mechanics at non-cosmological distances use Newton's full law? I am a scientist and I have never used it except to pass a college exam. I deal with chemistry and thermodynamics in which gravity is a negligible factor. PAR (talk) 16:58, 29 May 2021 (UTC)
Maybe I missed it, but @PAR, can you explain what's inadequate or inferior about the current wording and why it should be changed? -Jordgette [talk] 14:14, 29 May 2021 (UTC)

@Jordgette - At the beginning of the second paragraph it says: "Gravity is most accurately described by the general theory of relativity". I inserted "At present, gravity is....". It's not a huge deal, but the arguments against it are problematic to me. The reason I changed it was because it sounded like the final word on gravity has finally been found, and science never goes that far.

Also, I have a problem with "However, for most applications, gravity is well approximated by Newton's law of universal gravitation". I think this is parochial - In someone's own world, it may be true, In someone else's it wont be, and 99 percent of the use of the law of gravity is based on Galileo's assumption that gravity produces a constant acceleration, not Newton's law. I want to replace it with "general relativity is essentially equivalent to Newton's law for non-relativistic situations" which I think is more informative and not parochial. Going back and forth, there is what I think is a better version for the entire paragraph:

Newton's law of universal gravitation was the first scientific description of gravity, which described gravity as a force causing any two bodies to be attracted toward each other, with magnitude proportional to the product of their masses and inversely proportional to the square of the distance between them. Newton's law of gravitation has been superseded by the general theory of relativity (proposed by Albert Einstein in 1915), which is a more accurate and general theory of gravitation, and is essentially equivalent to Newton's law for non-relativistic situations. General relativity describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass. The most extreme example of this curvature of spacetime is a black hole, from which nothing—not even light—can escape once past the black hole's event horizon.

PAR (talk) 16:58, 29 May 2021 (UTC)

But gravity is most accurately described by GR, and gravity is well approximated by Newton's law for most applications. That language is plain, effective, and direct. Why weaken it and make it more wordy? "science never goes that far" — exactly. For that reason, "at present" is unnecessary and potentially confusing. It looks like you're a one-person minority opinion here. -Jordgette [talk] 18:41, 29 May 2021 (UTC)
Oh, I know I'm a one person minority, and I have no intention of editing the article unless that changes. But that doesn't mean I'm wrong. Maybe I am, and I will listen to arguments, but I won't listen to arguments that simply say I'm wrong.
What is the meaning of "gravity is most accurately described by GR"? To me that implies that it cannot be replaced by a more accurate theory, which is confusing at best and wrong at worst. I understand, the argument is that the statement IMPLIES "gravity is most accurately described by GR at the present time and may or may not be superseded in the future by something better", but that to say that is "awkward". I think the above paragraph is accurate, not awkward, and simply avoids making that controversial and confusing statement.
What is the meaning of "for most applications, gravity is well approximated by Newton's law of universal gravitation"? If we count up the number of times everyday people make use of the theory of gravitation, they overwhelmingly do not use Newton's law, they use the constant acceleration assumption, in which weight and mass are used interchangeably. How do you justify saying "for most applications, gravity is well approximated by Newton's law of universal gravitation"? Why not say the more informative and less controversial "GR gives practically the same results as Newton's law in non-relativistic situations"? That is a statement that won't be objected to by anyone, no matter what little technical world they live in.
I've tried to explain that this does not imply that every scientific article needs to be overhauled. Only when you are worrying about where a scientific theory fits into the big picture (like GR in the above statement), or comparing how two theories fit in the big picture (like Newton vs. GR), do you need to be concerned. If you say "its implied, end of story", then ok, end of thread. If you define "most applications" as "most applications except those of everyday people". then ok, end of thread. I'm not responding here with any expectation of changing the article, I'm learning how people view science and maybe altering my own, learning something, and maybe having them re-examine theirs. For example, I never considered the idea that every article would have to be overhauled, and since that's obviously crazy, I had to think about what I really meant to say, and in so doing refined my own understanding of what science is all about. "You are just wrong" is useless to me, I have way better things to do. PAR (talk) 22:03, 29 May 2021 (UTC)
PAR, I don't think our readers should need to know what a 'relativistic situation' is to understand the article lead. Simple language should be preferred whenever practical. MrOllie (talk) 22:24, 29 May 2021 (UTC)
Yes. Is there a way of saying it without using the term "relativistic situation"? Like "... which is a more accurate and general theory of gravitation. For most applications involving the calculation of the orbits of planets and other objects, the two theories give practically the same results, with some notable exceptions" PAR (talk) 15:13, 1 June 2021 (UTC)

Adjustment for centrifugal force seems suspect

I was annoyed that the article adjusted the force of gravity for centrifugal effects, since I'm interested in the force of gravity, not net forces of other kinds. So I tried calculating the actual force of gravity at the equator based on the force of gravity at the poles (where centrifugal effects are near zero) and adjusting for the distance from the core at the equator, per the square-inverse law.

The calculated purely-gravitational force at the equator came to almost exactly the force cited in the article for net gravitational and centrifugal effects. It was close enough that the difference falls below the threshold of the significant figures used.

Showing my math: http://ciar.org/h/82d6ee.txt

Is it possible that someone was just confused, and decided that since the widening of the earth at the equator is due to centrifugal effects, the force of gravity was also less due to centrifugal effects, and simply misrepresented the effect of the difference in distance?

TTK (talk) 18:32, 29 June 2021 (UTC)

So should the article call gravity a force or not?

I know there has been some discussion to remove references to gravity being a force, as it isn't a force according to general relativity. Why, then, does paragraph 3 refer to the fundamental forces and the strong force, when in fact those (redirected) articles are properly called Fundamental interaction and Strong interaction? Seems like this would be confusing to the reader who isn't sure what exactly gravity is. -Jordgette [talk] 14:03, 1 July 2019 (UTC)

The use of "force" is per Einstein-Cartan Theory, endorsed by Einstein thru written conversations with Cartan, about 14 years after Einstein's publication of General Relativity, and well before his loss to Bohr in the EPR Paradox discussions of the mid-1930's. ECT accomodates the concept of particulate spin (discovered in the mid-1920's), and GR can reportedly be derived from it, per the last (Version 26) Arxiv preprint of an article by Petti, subsequently published. It is widely reported to be more sophisticated (mathematically) than GR, and has allowed elimination of the cosmic "singularity", as described by Nikodem J. Poplawski in numerous papers preprinted on Arxiv between 2010 and 2020, several of which were subsequently published. The addition of Einstein-Cartan Theory to the list of active (not historical) "theories of gravity" is essential to the plausibility of the Wikipedia article "Gravity", and its current absence from that list renders the entire article questionable. — Preceding unsigned comment added by Ole Berson (talk • contribs) 15:52, 11 August 2020 (UTC)

A very interesting article is here on the matter of the matter

Nature Astronomy, 2019. DOI: 10.1038/s41550-019-0823-y Darwinerasmus (talk) 14:48, 14 July 2019 (UTC)

With link: Realistic simulations of galaxy formation in f(R) modified gravity. It is nice that it makes a testable prediction. We'll see what happens, for now it is still one of the more obscure approaches. --mfb (talk) 10:46, 15 July 2019 (UTC)

Yes, we should discuss it as both and make an important distinction between when it is applicable. Both frameworks of Newtonian gravity (using Newton's law) and General Relativity are import and valid ways to describe the effects of gravity. In many instances, only describing interactions with Newtonian gravity as a force is sufficient. i.e. you don't really need GR to describe what happens to a trajectory when you throw a rock out of a window. Additionally, you can describe a lot of large-scale structure formation in the universe with only Newtonian gravity Cosmojellyfish (talk) 21:18, 7 January 2020 (UTC)

I propose to clarify. There are no gravitational forces as such. Those forces that are called gravitational are forces of inertia, reactions from the forces of expansion of the Universe. The forces of inertia and "gravity" are a reaction from a combination of gyroscopic forces of rotation of electrons. Read the collection of articles "Physics of Gravity" published by Morebooks. Colnago2253 (talk) 19:17, 25 December 2020 (UTC)

Wikipedia is not the place to publish original research. -Jordgette [talk] 20:07, 25 December 2020 (UTC)

This requirement does not apply to talk pages Colnago2253 (talk) 13:01, 26 December 2020 (UTC)

Talk pages are there to improve the article. They are not the right place for OR either. --mfb (talk) 05:04, 27 December 2020 (UTC)

I briefly expressed my opinion on the topic, about article. Colnago2253 (talk) 07:55, 27 December 2020 (UTC)

The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing and forming stars and caused the stars to group together into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. Gravity has an infinite range, although its effects become weaker as objects get further away.

The above statement, while it likely sounds fascinating to the reader and grabs their attention, is not an observed phenomenon--scientists do not know that gravity created stars or galaxies or solar systems, etc. - this is not a data-substantiated claim but rather a belief/hypothesis. If this section is to be kept in any fashion at all, it needs to be restated to something like:

At present, it is believed the gravitational attraction of the original gaseous matter present in the Universe may have caused it to begin coalescing and forming stars and caused the stars to group together into galaxies. Though this hypothesis is yet to be confirmed, it would explain how gravity could have been responsible for many of the large-scale structures in the Universe and scientists today are continuing research to demonstrate the validity of this hypothesis. Gravity has an infinite range, although its effects become weaker as objects get further away. 155.188.123.52 (talk) 16:18, 8 July 2021 (UTC)RTP

How would that hypothesis ever get confirmed? One could also say that the formation of the planets in our solar system is only believed to have been caused by gravity, an unconfirmed hypothesis, as neither is planet formation by gravity an observed phenomenon. -Jordgette [talk] 22:03, 8 July 2021 (UTC)
155.188.123.52 is totally wrong. The central role of gravity in forming planets, stars, galaxies, and larger structures in the Universe is completely confirmed. It is the fundamental organizing principle of all astronomy, and as well established as any scientific fact. The formation of the Universe, called the Big Bang theory, and the central role of gravity in it, has been worked out back to the first few seconds, so well that we know the age of the Universe within one tenth of one percent. The life cycle of stars and how they form from gravitational attraction of interstellar gas and dust is known in great and excruciating detail. The formation of planetary systems from gravitational attraction of a protostar's nebula is similarly known. The formation and life cycle of galaxies is not known in as great detail, but that they too form and are held together by gravitational attraction has never been in doubt. Although astronomers cannot observe a single planet, star, or galaxy over a long enough time scale to watch these things happen, they are able to confirm these theories in detail because there are hundreds of billions of stars and galaxies visible to telescopes, in all stages of birth and death. --ChetvornoTALK 08:35, 9 July 2021 (UTC)

Semi-protected edit request on 29 September 2021

SilicanDefense (talk) 16:35, 29 September 2021 (UTC)


Gravity is more of a convention than a law

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. Cannolis (talk) 16:58, 29 September 2021 (UTC)

Wiki Education Foundation-supported course assignment

This article is or was the subject of a Wiki Education Foundation-supported course assignment. Further details are available on the course page. Peer reviewers: Catwilsonaz.

Above undated message substituted from Template:Dashboard.wikiedu.org assignment by PrimeBOT (talk) 22:38, 16 January 2022 (UTC)

Force?

… which describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime …time to get on board with this and stop promulgating the old ‘gravity is a force’ misconception 184.6.8.244 (talk) 12:20, 22 January 2022 (UTC)

Time to read the article. The second paragraph says: Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915), which describes gravity not as a force, but as a consequence of masses moving along geodesic lines in a curved spacetime caused by the uneven distribution of mass.
I have amended that to: Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915), which describes gravity not as a force, but as the curvature of spacetime, caused by the uneven distribution of mass, and causing masses to move along geodesic lines. - DVdm (talk) 12:32, 22 January 2022 (UTC)

Deleted section

I have just deleted the following section from the article, because it seemed irrelevant and tangential for the History section. I am leaving it here in case it makes sense for some of the content to be intgerated back in later:

Equivalence principle

The equivalence principle, explored by a succession of researchers including Galileo, Loránd Eötvös, and Einstein, expresses the idea that all objects fall in the same way, and that the effects of gravity are indistinguishable from certain aspects of acceleration and deceleration. The simplest way to test the weak equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the same rate when other forces (such as air resistance and electromagnetic effects) are negligible. More sophisticated tests use a torsion balance of a type invented by Eötvös. Satellite experiments, for example STEP, are planned for more accurate experiments in space. Formulations of the equivalence principle include:

  • The weak equivalence principle: The trajectory of a point mass in a gravitational field depends only on its initial position and velocity, and is independent of its composition.
  • The Einsteinian equivalence principle: The outcome of any local non-gravitational experiment in a freely falling laboratory is independent of the velocity of the laboratory and its location in spacetime.
  • The strong equivalence principle requiring both of the above.

Mover of molehills (talk) 15:33, 6 May 2022 (UTC)

Semi-protected edit request on 26 May 2022

"The gravitational attraction between the original gaseous matter in the Universe allowed it to coalesce and form stars which eventually condensed into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. Gravity has an infinite range, although its effects become weaker as objects get farther away."

Request to add the source of this explanation as a footnote. 119.95.247.39 (talk) 06:34, 26 May 2022 (UTC)

Please be more specific. What exactly do you want to add as source here? The lead summarizes the article so usually it doesn't need its own references. --mfb (talk) 10:11, 26 May 2022 (UTC)
 Not done for now: Per mfb. ScottishFinnishRadish (talk) 10:32, 26 May 2022 (UTC)

Removing unsourced content

The "Specifics" section seems like the place where the quality of the article breaks down. It appears filled with stuff that did not fit neatly anywhere else. For example, in the subsection "Gravity and astronomy", the second paragraph talks about gravity emerging in a currently unknown manner. This part appears in the lead. Seemingly to flesh this bit out, an entire unsourced paragraph which really does not add anything new and uses language like "Although we have not traveled to all the planets nor to the Sun, we know their masses.." has been written above. This whole paragraph I think could be removed.

Similarly, the next subsection "Gravitational radiation" consists of one sourced section (the third), two unsourced sections and one unsourced sentence. The first paragraph could probably go, the second needs sources and that last sentence might remain if provided with a source, but I question its notability.

The subsection "Equations for a falling body near the surface of the Earth" is entirely unsourced and really only brings upp isolated formulae. It seems to have been written only to justify the link to the article "Equations for a falling body", and the whole subsection could probably be removed.

In the subsection "Earth's gravity", the centre portion deals with introducing a value for g specific to a single latitude and then explaining what acceleration means (this last bit unsourced). Everything but the two first and the last paragraph could be removed here.

These are my thoughts at least, and I thought it best to leave them here to hear what you think. Thanks.--Ribidag (talk) 07:46, 3 June 2022 (UTC)

I agree. Many of those sections are no more than padding, and could be replaced by a "See also" link. If you want to do radical pruning, though, I'd suggest doing it piecemeal rather than as one huge edit so that anyone who wants to engage can do so point by point. MichaelMaggs (talk) 07:56, 3 June 2022 (UTC)
I have cleaned it up a little. However, I still feel like there must be some better way to include the information than a "Specifics" section of miscellaneous topics. Any ideas? Ribidag (talk) 08:58, 3 June 2022 (UTC)

Semi-protected edit request on 10 June 2022

hi team Wikipedia in the list of earth and environment specifically in gravity there is no reference to the Indian phylospher Baskaracharya who formulated laws of gravity these references can also be seen on Google Boombimdib (talk) 15:18, 10 June 2022 (UTC)

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate. ScottishFinnishRadish (talk) 16:28, 10 June 2022 (UTC)

What's the source for the gravity at the Equator?

The article nowadays say:

The force of gravity is weakest at the equator because of the centrifugal force caused by the Earth's rotation and because points on the equator are furthest from the center of the Earth. The force of gravity varies with latitude and increases from about 9.780 m/s2 at the Equator to about 9.832 m/s2 at the poles.

So, the proportion is 9780/9832 = 99,47%

That would be Equator respect Poles, due to EVERYTHING, Latitude and centrifugal force.

Ok. Radius at the Poles is 6356752. At the Equator is 6378137. Divide and square to get the % due to latitude. 0,9966471401² = 99,33%

So, I guess we need these calculations on the page and some source or some calculations to explain the 99,85% reduction due to Earth's rotation (the difference between 99,33% and 99,47%).

--77.75.179.1 (talk) 19:52, 26 May 2022 (UTC)

I added a "citation needed." But the calculation is more complex than yours, since you are assuming that the mass is distributed spherically and uniformly, and it isn't. -Jordgette [talk] 20:15, 26 May 2022 (UTC)

Force of Gravity=G.m1.m2/d² PriyanshuDas1 (talk) 05:12, 6 August 2022 (UTC)

Semi-protected edit request on 11 August 2022

Change "General relativity states that gravity acts on light and matter equally, meaning that a sufficiently massive object could warp light around it and create a gravitational lens. This phenomenon was observed for the first time in 1979, when the Hubble telescope saw two mirror images of the same quasar whose light had been bent around the galaxy YGKOW G1."

To "General relativity states that gravity acts on light and matter equally, meaning that a sufficiently massive object could warp light around it and create a gravitational lens. This phenomenon was first confirmed by observation in 1979 using the 2.1 meter telescope at Kitt Peak National Observatory in Arizona, which saw two mirror images of the same quasar whose light had been bent around the galaxy YGKOW G1." TenaciousDef (talk) 16:39, 11 August 2022 (UTC)

 Done. Added wikilink to Kitt Peak National Observatory and book citation [17]. - DVdm (talk) 16:55, 11 August 2022 (UTC)

Semi-protected edit request on 27 November 2022

Gravity, is the field created by both gluons quarks and starks that create either a proton or neutron. The bonds created between two atoms weak/strong nuclear force has some effect on the gravitational field while the sub atomic entanglement within the nucleus creates the majority of the gravitational fields. The pinch of the bonds between gluons, quarks and starks warp the space creating a field we know as gravity.

Christopher.Perkins26 (talk) 03:19, 27 November 2022 (UTC)

 Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format and provide a reliable source if appropriate.—Anita5192 (talk) 03:32, 27 November 2022 (UTC)
Let me be more direct: It's nonsense. --mfb (talk) 18:06, 27 November 2022 (UTC)
Stark, raving nonsense. EEng 18:26, 27 November 2022 (UTC)

The tides of the oceans

In the second paragraph, it says "and the Moon's gravity causes tides in the oceans".

I can't edit this page because it is a protected page but I am particular about details. I wonder, could someone edit for me?

The Moon's gravity is a cause of the tides, not the cause of the tides. The Moon's gravity causes one high tide per day but the other high tide of the day is caused by the inertia of the Earth and Moon orbiting one another. LeeMcLoughlinScientist (talk) 22:48, 2 October 2022 (UTC)

Done. I changed "causes" to "is largely responsible for". -Jordgette [talk] 00:35, 3 October 2022 (UTC)

The Moon is the dominant cause of all the tides but the Moon's gravity is the dominant cause of just half of them. The other high tides are caused by inertia. Thanks for the edit. LeeMcLoughlinScientist (talk) 22:20, 3 October 2022 (UTC)

Inertia only "causes" tides because the Moon's gravity is accelerating Earth, so I don't really see the point here. To make things worse, this idea of two tidal bulges is oversimplified to the point that it's not even a useful approximation. The real behavior is much more complex. Distinguishing between "tides caused by gravity" and "tides caused by inertia" makes no sense, it's always both together anyway. Your edit is still correct, but only because the Sun contributes 1/3 to the tides. --mfb (talk) 03:40, 4 October 2022 (UTC)
Agree with mfb --ChetvornoTALK 18:46, 27 November 2022 (UTC)
Technically, all mass external to the Earth contributes to the tides, but our sun and moon predominate.—Anita5192 (talk) 19:40, 27 November 2022 (UTC)

A Commons file used on this page or its Wikidata item has been nominated for deletion

The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:

Participate in the deletion discussion at the nomination page. —Community Tech bot (talk) 05:25, 8 December 2022 (UTC)

Can someone add the definition of gravitation?

Gravitation and gravity are not exactly the same, right? Since gravitation redirects here, the first paragraph should describe the two terms. Someone please add something to determine these two, even if they are the same or similar. Yyfroy (talk) 14:08, 25 February 2023 (UTC)

 Done—Anita5192 (talk) 16:02, 25 February 2023 (UTC)
Thank you for the added paragraph！Yyfroy (talk) 13:18, 26 February 2023 (UTC)
The OED defines gravity as: The attractive force by which all bodies tend to move towards the centre of the earth; the degree of intensity with which a body in any given position is affected by this force, measured by the amount of acceleration produced. Also often in wider sense, the degree of intensity with which one body is affected by the attraction of gravitation exercised by another body.
It lists two overlapping meanings of "gravitation": The attraction of one body for another, or the effective force of one body moving towards another; the tendency of every particle of matter towards every other particle, of which the fall of bodies to the earth is an instance, and also The action or process of gravitating; in early use, the falling of bodies to the earth or their sinking to their lowest level; in later use applied in wider sense to the process of which this is an instance, the moving or tending to a centre of attraction.
So both words can be used in a fundamental scientific sense which applies to all massive bodies, and to the earth as a specific example. The current lead focuses on the fundamental sense, which I think is right. MichaelMaggs (talk) 15:22, 25 February 2023 (UTC)
Thank you for your information. Yyfroy (talk) 13:16, 26 February 2023 (UTC)
In my opinion, under its current scope, the article should be renamed as "Gravitation" because that is the general term, it being the attraction between any two bodies like sun and the earth but also me and my laptop, while gravity is only a specific form of gravitation, that is the attraction towards the earth or celestial bodies. In Venn diagram sense, Gravity would lie entirely within Gravitation as a subset, so the article should be renamed, if not split. —CX Zoom[he/him] (let's talk • {C•X}) 11:52, 26 February 2023 (UTC)
The current title is the result of a move discussion 8 years ago (Talk:Gravity/Archive 8#Requested move 17 February 2015), but 8 years is enough of a time for consensus to change, so I'll be initiating a new Move Request, according to what the terms actually mean. Students or any general reader should not be misinformed about scientific terminologies when they use Wikipedia as their source for information. —CX Zoom[he/him] (let's talk • {C•X}) 11:57, 26 February 2023 (UTC)
I'm with you! Yyfroy (talk) 13:19, 26 February 2023 (UTC)
My original added paragraph is as below:
Gravitation is the force of attraction among objects that is caused by their mass, while gravity is the attraction of objects toward the Earth.<ref>Kurtus, Ron (2011). Gravity and Gravitation: Derivations, Equations and Applications. Lake Oswego, Oregon: SfC Publishing Co. pp. 25, 244. ISBN 9780976798163. Indeed, gravity is not limited to the Earth only. Yyfroy (talk) Yyfroy (talk) 13:25, 26 February 2023 (UTC)
Still another question:
In the first sentence, "In physics, gravity is a fundamental interaction which causes mutual attraction between all things with mass or energy."
Should we delete the last two words "or energy"? That sounds energy itself can attract another energy by gravity. Yyfroy (talk) 13:32, 26 February 2023 (UTC)
There was a lengthy discussion of this question, in 2016–2018, in Talk:Gravity/Archive_8#Opening_sentence_needs_reconsidering. I recommend removing it, for now, until someone can provide a reliable source. By removing it, we are not claiming that gravitation does not cause mutual attraction between things with energy.—Anita5192 (talk) 14:58, 26 February 2023 (UTC)
Thanks! That's a helpful discussion. Yyfroy (talk) 23:06, 26 February 2023 (UTC)

paradoxical intro

Gravity is, by far, the weakest of the four fundamental interactions, ... it has no significant influence at the level of subatomic particles. However, gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light.

(emphazis mine) weakest but most significant? in others words: weakest but strongest? This is so confusing, right in the intro. Either reformulate, or explain.

Besides, interactions have no strength per se that would allow this statement. Their strength depends on charge and distance. The "weakest" statement at (sub)atomic level just means particles have very low mass relative to charges of other interactions. The opposite being true at the macroscopic scale. Because mass scales up, while charges of other interactions cancel out, and also because of the way weak and strong interactions scale with distance (not in /r², but exponentially ).

May be it should be written:

Gravity has no significant influence at the level of subatomic particles, where it is, by far, the weakest of the four fundamental interactions: approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. However, gravity keeps growing in importance as scale increases; at human scale only electromagnetism still can be stronger; and at the scale of celestial objects gravity the most significant interaction between objects, and it determines the motion of planets, stars, galaxies, and even bend light. 2A01:E0A:1DC:4570:A44E:7BB5:529:4D19 (talk) 16:54, 16 April 2023 (UTC)

Speed of gravity/gravitational waves

The cited source is here. It's a press release rather than a peer reviewed paper, which is not ideal, but it does seem to support the assertion that gravitational waves travel at the speed of light. (The initial gamma-ray measurements, combined with the gravitational-wave detection, also provide confirmation for Einstein’s general theory of relativity, which predicts that gravitational waves should travel at the speed of light.) If this is an error, please provide a different source to support the changes you want to make.

Regarding the etymology stuff, I'm sorry that you think it makes the opening sentence look untidy, but it is very common in articles of this sort. You can make the case for its removal here, but you would need to get consensus for that. Likewise the addition of a paragraph on different ways in which gravity can be measured (although I'd suggest that, at four paragraphs, the lead does not need any more paragraphs per MOS:LEADLENGTH). Girth Summit (blether) 13:14, 18 April 2023 (UTC)

As I remember it, a Wikipedia article should really open with the article’s title. That is the first word or words of the article’s lead would repeat the article’s title. That is not the case here.
Of the many thousands of Wikipedia articles I’ve read since Wikipedia’s founding, where the etymology is relevant, there is usually a separate section on this.
I removed an uncited claim, one that had been flagged as requiring clarification. That is that energy is a source of gravitation. Whilst probably true, it was uncited and neither could I find a reliable source.
With regards to the speed of gravitational waves, this is measured by the rise and decay of gravitational waves as plotted on a graph. The steeper the curves, the faster the waves. Gravity has been proven to travel at c.
The paragraph you removed outlining the three ways in which gravitation is measured, could this be inserted into the section ‘Definition’? The oracle 2015 (talk) 13:30, 18 April 2023 (UTC)
There is guidance for how to write the first sentence of an article at MOS:FIRST. In this case, the word 'gravity' van have different meanings in different contexts - which is why we have Gravity (disambiguation), and why we star the sentence with 'In physics, gravity is...'. See equivalent wording at, for example, Evolution, Equation and similar articles.
I would not be averse to splitting the etymology out into a separate section - that would be preferable to just deleting it.
Someone adding a 'requires clarification' tag on an assertion is not an invitation to remove it. It isn't cited in the lead, but it may be supported by some of the citations in the body of the text, and even if it's uncited that doesn't mean that it needs to be removed if you don't think that it's wrong.
The cited source supports the assertion that gravitational waves travel at the speed of light. If you can provide another source that supports a change in the wording, please go ahead.
The paragraph you inserted had no citations. I would have no objections to something like that being added to the definitions section, if it were supported by citations. Girth Summit (blether) 13:47, 18 April 2023 (UTC)
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