Talk:Gravitational field

Gravity in QM ?

Should there be a section on gravity in quantum mechanics ? MP ^{(talk•contribs)} 19:25, 3 November 2007 (UTC)

To the extent that it is described by a field theory. I would have added the section on it myself, if I knew anything about it...Someguy1221 20:00, 3 November 2007 (UTC)

Is there something we don't know about Gravity

RE: Article in Astronomy Today - RE: Flybys not following predictions

Gravity begins at the center of the Earth and as you continue out it becomes progressively less and less. If a flyby goes into a position of less gravity, just by doing so, it should accelerate the speed of the flyby. What do you think. I can explain gravity further. spacechat@hotmail.com Galaxy2010 (talk) 19:00, 25 January 2010 (UTC)

Questions about gravity should be directed to the science reference desk, at WP:RD/s. This page is for discussion of the article itself, and not its subject. Someguy1221 (talk) 19:12, 25 January 2010 (UTC)

If gravitational fied is around,then why does the flame of a candle is always pointing in the upward direction?

Gravity is observed as an attractive force but is possibly a "push" force due to universal radiation (wind) similar to salar wind. See https://www.rangutan.eu/gravity-explained/ — Preceding unsigned comment added by 88.66.246.152 (talk) 13:03, 18 October 2020 (UTC)

It sounds like you are talking about Le Sage's theory of gravitation which is no longer taken seriously due to its many flaws. JRSpriggs (talk) 21:01, 18 October 2020 (UTC)

Force is NOT perceived subjectively.

This is pseudo-relativity at it's absolute worst:
"In a field model, rather than two particles attracting each other, the particles distort spacetime via their mass, and this distortion is what is perceived subjectively as a "force". In fact there is no force in such a model, rather matter is simply responding to the curvature of spacetime itself."

Force is not a subjective perception. The definition and units of force are defined by international agreement. In general relativity, gravitational force is measured with a spring scale.

The tired cliché "gravity is not a force in general relativity" is not even wrong. The correct concept is "gravity is a fictitious force in general relativity". —Preceding unsigned comment added by NOrbeck (talk • contribs) 14:33, 23 August 2010 (UTC)

Please sign your talk page messages with four tildes (~~~~)? Thanks.

We have sources saying that gravity is "no force", and that it is a "fictitious force" in general relativity, so it seems to depend on the author. By the way, I would not say that "gravitational force is measured with a spring scale". I'd say that "spacetime curvature is measured with a spring scale".

Anyway, the quoted statement is rather poor. I propose we say something like:

• "In a field model, rather than two particles attracting each other, the particles distort spacetime via their mass, and this distortion is what is perceived and measured as a "force". In fact one can state that is no gravitational force in such a model (ref 1), or that gravity is a fictitious force (ref 2), and that matter is simply responding to the curvature of spacetime itself."

DVdm (talk) 15:45, 23 August 2010 (UTC)

I went ahead and made some changes. The section is now properly sourced, so I have removed the tag. DVdm (talk) 09:26, 24 August 2010 (UTC)

Spacetime curvature is equivalent to the gravitational gradient (tidal acceleration); it is measured with a gravity gradiometer. Spacetime curvature is not measured with a spring scale, a spring scale measures the gravitational (pseudo) force. Uniform gravity does not imply curved spacetime, and zero gravity (e.g. at the center of the earth) does not imply flat spacetime. The topic at hand, the gravitational field, is measured with a gravimeter.

In classical mechanics, a gravitational field isn't a force field, but rather a specific force field. The force at a point in a gravitational field depends on the quantity of mass placed there, so gravitational force cannot be abstracted as a field.

In both theories, the concept of force is irrelevant when describing a gravitational field. Also, in metrical theories, the field quantity is usually the metric tensor. In that context, the derivative of the metric field is the equivalent of the gravitational field in Newtonian mechanics.

It is misleading at best to claim that "there is no gravitational force" in metric theories of gravity. I personally have been yelled at by engineers who feel that it is absurd to suggest that the quantity measured by a torsion balance (as in the Cavendish experiment) is not a force, and I agree 95%. One could just as easily argue that there is no gravitational acceleration in GR, or that there is no tidal forces in GR, or that there is no tidal acceleration in GR. The last statement is the most correct, since tidal acceleration in GR is caused by the curvature of spacetime, not a direct physical interaction.

Existing: "In a field model, rather than two particles attracting each other, the particles distort spacetime via their mass, and this distortion is what is perceived and measured as a "force". In such a model one states that matter moves in certain ways in response to the curvature of spacetime,[1] and that there is either no gravitational force,[2] or that gravity is a fictitious force.[3]"

Suggested: "In some field models, rather than two particles attracting each other, the particles distort spacetime via their mass, and this distortion is measured as an acceleration. In such models, one states that matter experiences accelerations due to inertial motion through curved spacetime."

For a related discussion see: Two-body_problem_in_general_relativity#Force_exists_in_GR. NOrbeck (talk) 09:06, 29 August 2010 (UTC)

I'd rather keep the existing formulation, the idea being not to formulate what we think is the best formuation, but just to show what is stated in the literature. In this regard I think we have 3 points of view (or better, formulations) from pretty solid sources. I do agree that the opening "In a field model" can be replaced with "In some field models". DVdm (talk) 11:09, 29 August 2010 (UTC)

In all formulations of all viable theories the concept of force is irrelevant to this article. Readers must be spared from trite philosphical digressions. NOrbeck (talk) 11:44, 31 August 2010 (UTC)

Yes, that is precisely why we can tell the readers how the "old gravitational force" is treated, and how various authors choose to call it informally. Some call it "no force" or a "fictitious force". I don't think that the cited authors are trite philosphers. DVdm (talk) 16:38, 31 August 2010 (UTC)

slight expansion

• added the gravitational field equations for both classical and GR,
• added some referances, hence removed the tag. Before I started there were still referances, so the tag wasn't even nessersary

-- F = q(E + v × B) 09:55, 18 December 2011 (UTC) removed the tag

The expansion became larger than I expected: some content ended up re-ordered, but I added 5 additional referances, and clarified all classical forms of the gravitational field equation, including the field due to a number of descrete external masses. I have a stomach-wrenching feeling the edits will be reverted just for that...-- F = q(E + v × B) 11:55, 18 December 2011 (UTC)

Definition of the gravitational field

If I remember correctly from my physics clases, the gravitational field is not just defined as Gravitational Force over a test mass but with a limit. Also, it is not any Gravitational Force -as it might be interpreted from the article-. I think it should be written as

${\boldsymbol {g}}=\lim _{m\to 0}{\frac {\boldsymbol {F}}{m}}$

where:

• m is the test mass
• F is the Gravitational Force between the mass that generates the field and the test mass JuancitoxTw (talk) 13:49, 18 July 2012 (UTC)

Generally accepted fundamental hypothesis

I think the citation from Jesse L. Greenstein in this article is very confusing and taken out of context. I learned about it from a question on Quora: Are gravitational waves the new (a)ether?, which links to this Wikipedia article. The analogy between gravitational field and ether is very far fetched and reflects the author's subjective opinion. I propose to remove the whole section.

Bartosz (talk) 22:00, 3 September 2013 (UTC)

Proposed merge of Non-Relativistic Gravitational Fields into Gravitational field

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

To not merge as proposed, but a sense that some action was warranted; Parameterized post-Newtonian formalism or Linearized gravity are preferred targets. Klbrain (talk) 09:32, 6 April 2023 (UTC)

---

The content of Non-Relativistic Gravitational Fields is currently highly-technical. Merging the article's content into Gravitational field and reviewing the content would make more sense. Also, isn't a non-relativistic gravitational field, well, a gravitational field? Singularity42 (talk) 12:28, 29 June 2022 (UTC)

These fields are not strictly non-relativistic. Rather, they apply to the non-relativistic limit of General Relativity. A note to this effect was added to the entry.

I believe that the entry is as technical as many of the other entries that it is linked with, within the General Relativity category.

Since the topic of Non-Relativistic Gravitational Fields belongs to General Relativity, I believe it would _not_ make sense to merge it into Gravitational field. Barak.K.huji (talk) 12:56, 29 June 2022 (UTC)

The article is no more an orphan, as 4 other articles link to it. In order to make it more accessible, it was supplemented with a gentle introduction, with a section on physical interpretation and more. Barak.K.huji (talk) 13:15, 29 June 2022 (UTC)

• Merge the article's content into Gravitational field. Its a sub-type of that and once you boil it down to encyclopedic content its going to be one paragraph. Fountains of Bryn Mawr (talk) 15:27, 29 June 2022 (UTC)

I oppose merger and suggest that Non-Relativistic Gravitational Fields be deleted. Alternatively it could be merged with Gravitoelectromagnetism, another useless article. Trying to treat gravity as derived from a vector field (as if it were electromagnetism) is wrong. If you do not want to go to full GR, then Linearized gravity or Parameterized post-Newtonian formalism is a better way to go. JRSpriggs (talk) 22:27, 29 June 2022 (UTC)

• Merge It definitely should be merged or deleted. But a better target would be one of the articles it is related to: Parameterized post-Newtonian formalism or Linearized gravity. Then it wouldn't require so much description, probably only a paragraph. --Chetvorno^TALK 00:21, 30 June 2022 (UTC)

• Comment - I would note that Barak.K.huji looks to be the writer ("Kol, Barak"?) of most of the papers cited in this article - maybe a move to Wikisource? Fountains of Bryn Mawr (talk) 15:45, 30 June 2022 (UTC)

  Good catch. I have tagged the article about the potential conflict of interest, and left a message on the user talk page. Singularity42 (talk) 16:37, 30 June 2022 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

This discussion is rather stale, so I've summarized what I can, then will start a new proposal based on the conclusions of the discussion here. Klbrain (talk) 09:32, 6 April 2023 (UTC)