Talk:gravity

serious behavior

solemnity and seriousness in somebody's attitude or behavior
Microsoft® Encarta® 2009

--Backinstadiums (talk) 11:17, 21 November 2019 (UTC)

You don't explain the mechanism of gravity

Some theories exist (generally accepted: wavefunctional entropy within a system constituted of more than one particles). Keep that issue open to be filled in the future. We are supposed to evolve our definitions (not immediately, and with facts). We aren't supposed to hide conundrums.

Middle vowel not a schwa?

Equinox ◑ 13:34, 15 July 2021 (UTC)

Physics

The definition as I found it was terrible:

(physics) The force at the Earth's surface, of the attraction by the Earth's masses, and the centrifugal pseudo-force caused by the Earth's rotation, resulting from gravitation.

• Different objects subject to the same gravity experience different forces. Gravity is the phenomenon that objects experience downwards forces, not an individual force.
• Terrestrial gravity does not only apply at the earth's surface. Aeroplanes and miners, for instance, are both subject to it.
• Why the plural 'Earth's masses'?
• Terrestrial gravity has *absolutely nothing* to do with 'centrifugal pseudo-force caused by the Earth's rotation'.

I've respected the existing distinction between terrestrial gravity and celestial gravitation. Since Newton, these two observable phenomena have been recognised as manifestations of the same universal law, termed either 'gravity' or 'gravitation'. However, prior to Newton, there were earlier theories of gravity (by Aristotle or Galileo, for instance) which only accounted for terrestrial gravity.

All that said, I'm new here, and I'm sure my attempt can benefit from revision. I believe it's better than what I found, though. Rural Spaceman (talk) 12:29, 28 August 2024 (UTC)

Looking back in history, I can see where the 'centrifugal [...] resulting from gravitation' wording came in.

> Resultant force on Earth's surface, of the attraction by the Earth's masses, and the centrifugal pseudo-force caused by the Earth's rotation (https://en.wiktionary.org/w/index.php?title=gravity&oldid=12686)

Here, the term 'resultant' is a technical one, referring to the overall force found to be acting on an object when several contributory forces have been added up. This has later been misinterpreted by a non-technical contributor as referring to causation, and hence replaced with the phrase 'resulting from'. (https://en.wiktionary.org/w/index.php?title=gravity&diff=58843119&oldid=58564172)

There are two ways of looking at terrestrial gravity, in the earth's rotating frame of reference:

1. masses experience two forces, gravitational and centrifugal, and 'gravity' refers to the sum of the two

2. masses experience those two forces, and 'gravity' refers only to the former.

In case 1, we would say that gravity at the equator is weaker than at the poles; in case 2, we would say that gravity at the equator is counteracted in some small measure by centrifugal force. I don't know that English usage favours either interpretation over the other. I would suggest that this is a fitting subject to discuss in an encyclopaedia, but that a dictionary should steer clear.

(Re centrifugal force vs pseudo-force: https://xkcd.com/123) Rural Spaceman (talk) 08:42, 5 September 2024 (UTC)