Timeline for Why doesn't the Moon fall onto the Earth?
Current License: CC BY-SA 3.0
23 events
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| Apr 3 at 20:33 | comment | added | Ed999 | @Harvey The Moon's velocity is balanced against the Earth's gravity: initially, the Moon's distance from Earth (its altitude) increases until the Moon's forward velocity is exactly equal to the opposed forces (created by the Earth's gravity), which increase as altitude increases, so that it can't gain any more altitude. If its velocity was greater, its altitude would also be. Gravity is poorly understood by the layman: its real effect is to modify the resistance of spacetime to a moving object but unlike air resistance it doesn't bleed off velocity, because there is no exchange of energy. | |
| Jan 21, 2022 at 23:31 | comment | added | Harvey | I think the answer is very comprehensive. However I’m still unsure whether it answers the essence of the question. Which is really about the equilibrium of the forces. Why are they so balanced and surely they were in a less balanced state and therefore one would override the other. It’s the pure equilibrium that baffles me | |
| Sep 30, 2019 at 20:07 | comment | added | Ed999 | Momentum ceases to be a simplistic matter of mass multiplied by velocity, because, in a gravitational field, velocity is a variable factor, dependent upon the particle's location within the field. It is only mass which is genuinely invariant. The field's response is varying with distance from the centre of the mass generating it, and with the angular motion of the particle. Momentum is a variable factor, varying with velocity, which in turn is varying with the condition (the "response") of the field. | |
| Sep 30, 2019 at 19:53 | comment | added | Ed999 | Einstein rejected Newton's theory as too simplistic, and we should be wary of rejecting Einstein's deeper insight into the principles of gravitation. | |
| Sep 30, 2019 at 19:41 | comment | added | Ed999 | Newton theorised that an object in motion (e.g. a particle) will continue that motion unless acted upon by a force, known as "conservation of momentum". That theory nevertheless conflicted with his theory of gravitation, in which a particle accelerates in a gravitational field without any application of force (if by force we understand him to mean an injection of energy). It is the medium's response to that momentum which changes. | |
| Sep 30, 2019 at 19:32 | comment | added | Ed999 | The answer contains a flaw (not in the logic borrowed from Newton!), in that paragraph 4 talks about "dropping" the rock. But this subsequently becomes a (mysterious) "downward force". If the rock is hurled downwards, I can see a force; but not if it is merely dropped. The rock, logically, merely follows the path of least resistance (when released). Gravity might superficially resemble a force, but really no force in the usual sense is being applied. Only a reduction (at the quantum level) in the resistance of the medium in a specific direction, caused by the presence of mass. | |
| Sep 11, 2016 at 23:42 | history | rollback | Mark Eichenlaub |
Rollback to Revision 3
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| S Sep 11, 2016 at 18:37 | history | suggested | MrAP | CC BY-SA 3.0 |
fixed grammar
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| Sep 11, 2016 at 17:54 | review | Suggested edits | |||
| S Sep 11, 2016 at 18:37 | |||||
| Jun 16, 2016 at 15:27 | comment | added | Luaan | @sabotero In newtonian physics, Earth's gravity is exactly the thing that keeps the Moon in orbit - that's what curves its path. Tidal forces do slow down the Moon, but at the same time, it moves on a wider orbit, so it stays in a circular orbit. In fact, that's how Moon's rotation got synchronized to Earth's in the first place (that's why you can only see the near side of the Moon, give or take 5% of surface area). Eventually, this would cause the Earth to also become locked to the Moon's rotation if we could ignore a few things that mess this up. | |
| Apr 29, 2015 at 7:41 | comment | added | Joe | If the earth suddenly disappeared, the moon would continue in a straight line. The earth's gravity pulls the moon's straight path into a curved arc. | |
| Apr 29, 2015 at 7:08 | comment | added | sabotero | @Joe, well, i don't know, doesn't she? There are others forces like earth gravity. I was seeking for an explanation for why actually she does not lost speed, is she accelerated at each turn around the earth? | |
| Apr 28, 2015 at 17:39 | comment | added | Joe | @sabotero, why would the moon lose speed? There's no air friction to slow it down. | |
| Feb 25, 2015 at 9:25 | comment | added | sabotero | Indeed, most illuminating answer. That rise another question to me, why does not the moon (or another large body) lost the speed needed to be in orbit (other than resistances forces). Or does she, the moon lost speed? | |
| Oct 9, 2014 at 9:18 | review | Suggested edits | |||
| Oct 9, 2014 at 10:19 | |||||
| Jan 15, 2013 at 14:09 | comment | added | user11266 | It is indeed contradictory. "Falling to Earth" and "crashing into Earth" are two entirely different things. A ball can fall without crashing into Earth, but it cannot crash into Earth without first falling. Words, especially in physics, must be as unambiguous as possible. And by the way, I'm quite cognizant thank you. | |
| Jan 14, 2013 at 20:45 | comment | added | Mark Eichenlaub | No, it doesn't contradict itself. "Fall to Earth" means, to any cognizant reader, the same as "crash into Earth" in that sentence. Further, this phrasing mimics the language of the question. Words like "fall" can mean different things in contexts. Most people are able to understand this. | |
| Jan 14, 2013 at 17:05 | comment | added | user11266 | The first sentence contradicts itself in that orbital motion is a state of free fall toward the center of attraction. Then, in the final paragraph, the first sentence contradicts the very first sentence. A beginner would have a difficult time with this logic. | |
| Dec 15, 2012 at 16:57 | review | Suggested edits | |||
| Dec 15, 2012 at 17:30 | |||||
| Jun 27, 2011 at 5:53 | history | edited | Mark Eichenlaub | CC BY-SA 3.0 |
deleted 1 characters in body
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| S Apr 24, 2011 at 19:40 | history | suggested | CommunityBot | CC BY-SA 3.0 |
Fixed a typo - "The Earth falls toward the Earth" should be "The moon falls toward the Earth"
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| Apr 24, 2011 at 15:30 | review | Suggested edits | |||
| S Apr 24, 2011 at 19:40 | |||||
| Apr 24, 2011 at 6:48 | history | answered | Mark Eichenlaub | CC BY-SA 3.0 |