Talk:Gravity

"Earth's gravity" section

What is the statement

If an object with comparable mass to that of the Earth were to fall towards it, then the corresponding acceleration of the Earth would be observable.

supposed to mean?

"comparable" and "observable" seem pretty fuzzy (are the moon or the sun of "comparable" mass? Remembering that they both contribute to tides --and are falling toward the Earth--. The tides are obviously "observable", but what about the acceleration that cause them?). And the mass of the object is not the only things that matters, its distance is even more important.

Likewide,

The force of gravity is weakest at the equator because...

well, the earth is not perfectly round because of the centrifugal force, so this force and the fact that "points on the equator are furthest from the center of the Earth" are a single and same phenomenon, isn't it? So it doesn't add with itself; you can explain lower gravity at the equator either way (centrifugal or "further from the center") but not in a way that seems additive.

More troubling, digits don't add up well. Polar radius of 6357 km Vs an equatorial radius of 6378 km, an object at the equator is 21 km (0.33 %) farther from the center than at the pole, which translate into a gravitational force 1.0066 smaller (1.0033 squared); 9.832/1.0066=9.767 , so if g at the pole is indeed 9.832, then at the equator it should be close to 9.767 instead of the claimed 9.780. I wouldn't argue if 2 digits after the comma were used (9.77 is close enough to 9.78), but the use of 3 digits imply an accuracy that seems absent. 2A01:E0A:1DC:4570:8186:825A:26A:E47C (talk) 17:16, 19 April 2023 (UTC)

• The image with caption "If an object with comparable mass to that of the Earth were to fall towards it . . ." is illustrating Newton's 3rd law of motion. With ordinary sized falling objects on Earth, it looks as if the Earth is stationary and only the object moves. But actually in the center of mass frame, as the falling object moves toward Earth, the Earth moves slightly toward the object. With a heavy enough object the acceleration of the Earth would be measureable, as shown in the video. I'm not sure what relevance this has to the subject.

• "Well, the earth is not perfectly round because of the centrifugal force, so this force and the fact that "points on the equator are furthest from the center of the Earth" are a single and same phenomenon, isn't it?"

No, they are not exactly the same phenomenon. If the Earth was solid, not made of liquid magma, and spherical, gravitational acceleration would be the same at any point on the surface even if it was rotating. The force on a surface object would still be slightly less at the equator than at the poles, because the gravitational acceleration would be reduced by the outward centrifugal force on the object, but according to https://pwg.gsfc.nasa.gov/stargaze/Srotfram1.htm the difference is only 0.346%. The measured gravitational acceleration at a point on Earth has two contributions, the gravitational field of the Earth, which depends on the distance to the center of the Earth, and the vertical component of the centrifugal force. Maybe that is the reason for the numerical discrepancy you noted. --Chetvorno^TALK 00:22, 20 April 2023 (UTC)

Da Vinci Pitcher Experiment

https://www.nytimes.com/2023/02/17/science/leonard-da-vinci-gravity.html

https://direct.mit.edu/leon/article-abstract/56/1/21/113863/Leonardo-da-Vinci-s-Visualization-of-Gravity-as-a

Da Vinci identified gravity as an acceleration before Newton, as evidenced by his right-angle triangle + pitcher diagram. 2A02:C7C:C4CD:A500:29E7:28A1:323E:45C (talk) 10:00, 11 June 2023 (UTC)

"Gurutvakarshana"

In the history section it is mentioned that Brahmagupta "proposed the idea that gravity is an attractive force that draws objects to the Earth and used the term gurutvākarṣaṇ to describe it"". But none of the three sources mentions the original verse where the word was used. can anyone clarify or change the sources where the exact word was used? ChandlerMinh (talk) 14:13, 14 September 2023 (UTC)

The Pickover book mentions Brahmagupta and the Sanskrit term. This secondary source is sufficient for the inclusion in the article. It would be ok to include a ref to the primary source, the "original verse where the word was used", but it is not required for Wikipedia. Johnjbarton (talk) 17:08, 11 November 2024 (UTC)

Semi-protected edit request on 11 November 2023

'See also' Under the 'See also' heading, items are no longer in alphabetical order. There now exists a duplicate item of Weightlessness On 19 June 2023 they were correct. It was modified from Micro-g environment. Can someone correct this please ? ie. Change 'Weightlessness' (1st occurrence) back to 'Micro-g environment' 110.175.165.80 (talk) 00:04, 12 November 2023 (UTC)

 Not done: Micro-g environment is simply a redirect to weightlessness. I've removed the first entry and moved the comment to the second. Liu1126 (talk) 00:22, 12 November 2023 (UTC)

Thanks for cleaning up the 'See also' section... 110.175.165.80 (talk) 00:34, 12 November 2023 (UTC)

Free fall

weight of freely falling body is zero then what heppens to the mass of object. I had observed that the weight of freely falling body doesn't become zero Muneer Ahmad Shiekh (talk) 15:23, 9 January 2024 (UTC)

To paraphrase the article, weight, "Some define weight as the magnitude of the reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale. In that sense of weight, in a state of free fall, the weight would be zero. Terrestrial objects can be weightless. So if one ignores air resistance, one could say the legendary apple falling from the tree, on its way to meet the ground near Isaac Newton, was weightless." Note also that the mass of the object is still there.—Anita5192 (talk) 15:39, 9 January 2024 (UTC)

Although this is Wikipedia:Notaforum, I will make the distinction between “weight” and mass. Mass does not ever change (except due to special relativity); if I have a mass of 70 kg, I will have a mass of 70 kg everywhere in the Universe. My weight is a measurement of how much force gravity is exerting on me. Technically, I would weigh 686 newtons - that is, gravity pulls on me with a force of 686 newtons. On Earth’s surface, at least; on the Moon, I will weigh less because gravity is weaker there, and in the clouds of Jupiter, I will weigh more because gravity is stronger there.

Basically, “mass” is independent of position and is an intrinsic quantity of much matter, while “weight” is the amount of force being exerted by gravity on that mass. OverzealousAutocorrect (talk) 18:13, 14 February 2024 (UTC)

Wiki Education assignment: 4A Wikipedia Assignment

This article was the subject of a Wiki Education Foundation-supported course assignment, between 12 February 2024 and 14 June 2024. Further details are available on the course page. Student editor(s): Jtolentino12 (article contribs). Peer reviewers: Nohemi1234.

— Assignment last updated by Ahlluhn (talk) 00:58, 31 May 2024 (UTC)

Hi! Editing an article like Gravity can be a big and challenging task. I wish you the best of luck. A while ago, I put together a page of general advice about writing physics and mathematics material on Wikipedia that may be helpful. XOR'easter (talk) 04:21, 19 March 2024 (UTC)

Mutual Interaction Between Massive Objects

This article starts with following statement:

" In physics, gravity (from Latin gravitas 'weight') is a fundamental interaction which causes mutual attraction between all things that have mass."

We all know that gravity is defined as the interaction between massive objects in terms of Newton. But observations and theory of Einstein shows that even light ( which has no mass ) interacts with the space time curve called gravity. That implies we no longer say it is the mutual interaction between massive objects. Can we ? αμαλ (talk) 05:50, 20 April 2024 (UTC)

I would surmise it's fine for the first sentence of an encyclopedia article. For our purposes using human language to describe very abstract phenomena, the use of causes attraction in context gets filed under "not wrong" for me, though one would love to quibble over the implications of both words. Remsense诉 05:55, 20 April 2024 (UTC)

@Remsense, So you are telling me that it makes easy to understand, right?

You should check following article by nasa: “ Gravity is the force by which a planet or other body draws objects toward its center. The force of gravity keeps all of the planets in orbit around the sun” it clearly states the purpose of gravity, but doesn't confuse people who are getting started with physics. Because, if a kid browse for the gravity - the search result of Wikipedia provides an outdated information, then what's the actual purpose of Wikipedia: The Encyclopedia itself. αμαλ (talk) 06:12, 20 April 2024 (UTC)

Well, that's the "purpose" in the context of planetary systems, which makes sense for an explanation by NASA. Otherwise, I'm not sure what point you're making—I think our lead does a good job at broadly surveying the important aspects of the topic from all the relevant perspectives. Remsense诉 06:18, 20 April 2024 (UTC)

I think the first sentence is correct enough. The first sentence does not need to list all possible results of gravity. It does not, in fact, says that gravity is the mutual interaction.

If we want to avoid Newtonian bias then I suggest focusing on the word mutual. In general relativity independent mutual interactions are replaced by an indirect spacetime distortion.

In terms of importance, I think the intro should start with phenomenology and then Newton and then general relativity. The comparison to other forces is a detail that should come later. Johnjbarton (talk) 15:55, 20 April 2024 (UTC)

I Agree with You. As a matter of fact, I was pointing to mutual Interaction of masses. If it simply says - the mutual interaction - it will be correct statement with both of these theories. αμαλ∆ 14:20, 21 April 2024 (UTC) — Preceding unsigned comment added by Amalvelloor (talk • contribs)

Sorry, we don't agree. "the mutual interaction" would not be more correct if your goal is to include general relativity. Please see Mass in general relativity. The issue isn't that light interacts but does not have rest mass, but rather the concept of "mutual" relies on identifying locations and observers that can't be done in general relativity.

I think a better fix here is a second sentence that highlights both the amazing accuracy of Newtonian gravitation and the correction added by general relativity.

The rest of this article needs work. Johnjbarton (talk) 15:14, 21 April 2024 (UTC)

Definition

I think the current definition of gravity as a "fundamental interaction which causes mutual attraction between all things that have mass" is misleading and incomplete, as for instance light has long been proven to be affected by it. Though the first definition of an article should be concise and simple, it should also be an accurate statement that best reflects our up-to-date scientific understanding of the phenomenon, even if it means for it to be defined in accordance with general relativity. 31.4.136.20 (talk) 12:46, 10 August 2024 (UTC)

The very best way to make your case is to cite a reliable secondary source.

It's not practical to include a complete description of general relativity in the first sentence. We could go with "fundamental interaction primarily observed as mutual attraction between all things that have mass" Johnjbarton (talk) 16:19, 10 August 2024 (UTC)

Agree with John. I just wanted to mention for others: mainstream media articles like Einstein showed Newton was wrong about gravity. Now scientists are coming for Einstein. NBC News are not reliable sources on scientific topics, and particularly not on what is WP:DUE WEIGHT for new scientific discoveries. Newsmedia report on what is new and different, from WP:primary sources, while science is a consensus process, and new theories are not accepted until they have been confirmed and appear in WP:secondary sources. This is a continuing problem on WP; editors without a scientific background read the latest news article about a new discovery and are determined to insert mention of it in the article, as here. --Chetvorno^TALK 18:07, 10 August 2024 (UTC)

I agree with the principle of only including information that is part of the scientific consensus and has been confirmed by secondary sources. However, I am unsure of what you are suggesting in this case.

If you believe general relativity is not mainstream and part of the scientific consensus, the article on the topic states that this theory "is the current description of gravitation in modern physics." Furthermore, there is an entire page on empirical evidence that supports Einsten's theory.

If, on the other hand, the scientic community deemed general relativity as a hypothetical reference model, or the current evidence were not considered strong enough to make the theory mainstream (at least by WP standards), the current articles on the topic would need to be updated.

The definition suggested by @Johnjbarton seems to be more appropriate than the current, as it leaves room for relativistic interpretation without delving into its details upfront. It is also a more circumspect claim, as it describes gravity as an observed phenomenon rather than a causal interaction. Viktaur (talk) 10:40, 11 August 2024 (UTC)

@Viktaur I guess there might be a bit of confusion here due to my edit just before @Chetvorno posted to this topic. I reworded a phrase that was incorrect and was sourced to a NBC site. I think we all agree that this is not a great source. I noticed the issue while looking to see what the article said related to the lead.

I will go ahead with my proposed change.

Based on a quick look it seems this article needs a little work. It has too much content on alternatives to general relativity. That work is both interesting and important but what we need in this article is to set the alternative work in context not enumerate all of the many players. Johnjbarton (talk) 16:24, 11 August 2024 (UTC)

@Viktaur @Johnjbarton Sorry, ignore my last post. I was in a hurry and misread the last few edits. I have no major problem with your changes. --Chetvorno^TALK 10:32, 12 August 2024 (UTC)