Talk:Gravitational potential

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This article was nominated for deletion on 22 March 2009 (UTC). The result of the discussion was no consensus.

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Archive 1

Issues with recent edits

The material on supernovae seems to be quite out of place. Indeed, it's relevance to the subject of this article seems tenuous at best. I have removed it, pending further justification as to what it has to go with this article. Secondly, I have only ever seen the term "gravitoelectric potential" in connection with general relativity. It is certainly not a term that is in wide use deserving of a place in the lead of the article. If having it in the GR section is not agreeable, then the article doesn't need to mention it at all. Sławomir Biały (talk) 19:58, 6 March 2012 (UTC)[reply]

You don't have a clue what you are talking about, which makes your tampering with the physics article irrelevant at best. U5ard (talk) 20:15, 6 March 2012 (UTC)[reply]

Well, the sources you give are unreliable for the content you have added. I have contacted the physics project here. We'll see what they say about it. Sławomir Biały (talk) 20:21, 6 March 2012 (UTC)[reply]

Also, if you have nothing constructive to add to this discussion (rather than ad hominem personal attacks), the default position is for us to restore the article to its original state (see WP:BRD). Quite frankly, this doesn't pass the smell test. While it's true that I'm not currently a practicing physicist, I do have a degree in physics. "Gravitomagnetism" has always been associated with fringe physics for me. Your section does little to alleviate this concern. If, as indeed you believe, this is supposed to be a mainstream interpretation of where the gravitational potential comes fr, then why are you referencing a self published source, and a book about supernovae that doesn't seem to address directly the point that you are making. Find a clear statement in the peer-reviewed published literature that supports your theory that the gravitational potential in the result of constructive interference on matter waves. Otherwise is is nothing more tgan original research. Sławomir Biały (talk) 20:32, 6 March 2012 (UTC)[reply]

I had a look at https://sites.google.com/site/eschatopaedia, which is used a few times as a source here. Clearly this is not anywhere near a wp:reliable source. Anything in the article that is referenced by this source, can be safely removed. I have reverted to an earlier version, and removed another statement in the image caption with eschatopaedia as a source. User U5ard (talk · contribs) warn on talk page. - DVdm (talk) 20:50, 6 March 2012 (UTC)[reply]

U=-mu/r is just an approximation

My professor mentione in class today that U=-mu/r is just an approximation of Laplacian(U)=0. However, I failed at locating and information on this. Does anyone know more and could add this? — Preceding unsigned comment added by 82.139.125.186 (talk) 19:13, 26 June 2012 (UTC)[reply]

The Laplacian of U is a multiple of a delta function. See Newtonian potential. This corresponds to taking a unit mass and placing it at the origin. Sławomir Biały (talk) 19:51, 26 June 2012 (UTC)[reply]

Definition of gravitational potential

I changed the definition of gravitational potential from work that is done per unit mass by the force of gravity to work that is done per unit mass by an external agent against the force of gravity. If it were to be work that is done by the force of gravity, then it would be positive since the direction of the gravitational force (towards the centre of the object) is the same as the direction of the displacement (towards the centre of the object as well). It is because gravitational potential is defined as the work that is done against the force of gravity (by something) so that the direction of the force is the opposite of the direction of the displacement and that gravitational potential is always negative.121.6.218.21 (talk) 08:58, 12 June 2015 (UTC)[reply]

Moving an object to infinity is against the force of gravity. Sławomir Biały (talk) 16:55, 12 June 2015 (UTC)[reply]

Sourced mathematical form

Twice ([1], [2]) the opening sentence of the section mathematical form was changed. I changed it back to the (triply) sourced version: [3], [4], [5], all litterally supporting the standing version. I think these sources speak for themselves, so I have accommodated the lead. Good point, JRSpriggs and Goodphy, but let's make sure we follow the cited sources as closely as possible - DVdm (talk) 06:39, 4 October 2016 (UTC)[reply]

Quite notably, those references (all based on the (British) A-level curriculum, and in that sense one source) neglect to say who is doing the work. For their definition to make sense this has to be taken as an external agent (this might be clear in the context of the A-level curriculum). Quite clearly the work done by the gravitational force in moving a unit mass from infinity to a point x is a positive number. I am going to hunt for some clearer references on this as the current state of affairs is most confusing for potential readers. (pardon the pun)T R 08:56, 4 October 2016 (UTC)[reply]

One thing that I dislike is that in defining it as the work done by an external agent no reference is made to gravity. I would much prefer (the clearly equivalent) definition as "the work done by the gravitational force on a unit mass at position x, if it were moved to infinity" (Besides having the advantage of stating clearly the relation with gravity, this also helps clarify the term "potential", which is short for potential to do work.T R 09:11, 4 October 2016 (UTC)[reply]

Looks good now.

@JRSpriggs: I undid your edit, because F is not "the force necessary to overcome the gravitational force, i.e. the negative of the gravitational force". It is just the expression of the gravitational force as a function of location. The integration is taken from infinity to some x. See F_G in the cited source Arfken and Weber on page 72. - DVdm (talk) 09:26, 5 October 2016 (UTC)[reply]

To DVdm: TimothyRias's version appears to be correct and is equivalent to mine. Your version has the wrong sign on the term including F. I suggest you look at your own source again. JRSpriggs (talk) 14:56, 5 October 2016 (UTC)[reply]

Tricky, these signes here. Better still, now. - DVdm (talk) 15:27, 5 October 2016 (UTC)[reply]

Chapter "Numerical values

Normally we don't talk about absolute value of gravitational potential, only the difference between two values. Also with "The potential is half the square of the escape velocity" a reader might get the impression that the potential increases deeper down in the gravitational well - (+) and (-) reversed. Hilmer B (talk) 21:11, 10 February 2017 (UTC)[reply]

This entire section seems to be original work. If so, that is a problem. As I write this, Voyager 1 is 20.6 Gkm from the Sun and Earth (20.63E9 & 20.61E9 km resp.)(according to the NASA site) yet the table claims it is 17 Gkm from Earth. Add these two problems to the problem mentioned by Hilmer B, that the absolute gravitational potential isn't known, and this entire table is very misleading. One other problem I have with it. Do these numbers include the contribution of Dark Matter? I doubt it. This section should be removed or completely rewritten, with authoritative references.40.142.183.194 (talk) 23:14, 25 February 2017 (UTC)[reply]

Fundamental Problem with this article.

There seems to be a fundamental problem with this article. In order to calculate the absolute gravitational potential at a point, contributions from ALL matter would have to be included. Also, given that matter isn't distributed homogeneously, the potential differs by direction of travel (less work would be required to separate a unit mass from Earth if the Sun or Moon were in the direction of (initial) travel). I'm not familiar enough with GR to say, but I'd guess that the tensor doesn't suffer from this (pretty severe, imho) shortcoming. In all situations where I've seen the term used, it is the potential DUE TO A reference mass (or system of masses, or mass distribution) and IGNORES the other masses, even if they contribute MORE to the total (absolute) potential (eg in near Earth problems, we calculate the gravitational potential on Earth's surface, usually ignoring the Sun's (or the Milky Way's) contribution.) So the definitions are wrong (or fatally incomplete).— Preceding unsigned comment added by 40.142.183.194 (talk) 23:37, 25 February 2017 (UTC)[reply]

Also, the top diagram of the potential vs over an x-y cross-section has a problem. The text states that the potential varies LINEARLY with distance below the (object's) surface. This is clearly NOT the case in this diagram, where the potential is everywhere curved (arguably with the exception of AT the surface). This diagram seems to be very wrong, I challenge its inclusion here.40.142.183.194 (talk) 23:37, 25 February 2017 (UTC)[reply]

As the article says, the force varies linearly inside a ball of constant density. The potential varies quadratically. The article is OK. JRSpriggs (talk) 01:36, 7 November 2019 (UTC)[reply]

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Merger from Gravity well

Hi there! I just stumbled over the article gravity well which was supposedly merged here last year. Now I want to point out that the merger should have in my opinion left some mention of the term/concept "gravity well" in this article.

Since I didnt participate in the merger and have not proper knowledge about the specifics of the concepts at hand I have to ask others to look into this.

Thanks! Nsae Comp (talk) 06:25, 12 February 2021 (UTC)[reply]