Sun-Earth-Moon Gravity

Sun cannot pull away Moon from Earth because of the following condition:The difference of gravitational accelerations caused by Sun on Moon to that caused by Sun on Earth is less than gravitation acceleration caused on Moon by Earth.I.e.,Acclelration due to gravity of Sun on Moon - Acceleration due to gravity of Sun on Earth < Accleration due to gravity of Earth on MoonThat is why Moon still orbits Earth without settling in an independent orbit of its own like that of Mars.In other words while orbiting around Sun, both Earth and Moon are accelerating towards Sun without much difference in their individual accelerations.When we are talking about differences in gravitation acceleration over distances, we are basically talking about tidal forces.

Tazmanian Devil, you need to think more on what I wrote. This is not something which just came out of my mind but is the exact scientific explanation.Yes, Moon does orbit the Sun, but that is not my point, it doesn't have an independent orbit like that of an asteroid or a planet. In fact it is part of gravitationally bound Earth + Moon system which together orbit the Sun. So there is a difference in having an independent orbit or orbiting by being part of a gravitationally bound system.If a gravitationally bound system like Earth and Moon have to separate by a force external to this system (like Sun's gravitational force), it is not the intensity of Sun's force on any particular body - Moon or Earth that counts. So even if Sun pull's Moon twice as stronger than that of Earth on Moon, still the Moon does not need to separate from Earth.It will separate only if the tidal forces of Sun on Earth-Moon system trying to pull away Moon from Earth are stronger than the gravitational force of Earth on Moon. In other words both Earth and Moon are accelerating towards the Sun, it is the difference in the acceleration, i.e., the net acceleration of separation of Moon from Earth due to Sun (in other words tidal force) that counts. This should be greater than the acceleration due to gravity that binds Moon to the Earth.Tidal force of Sun separating Moon from Earth = Mass of Moon * ( accln due to gravity of Sun on Moon - accln due to gravity of Sun on Earth). This tidal force should be greater than the gravitational force that binds the Earth and Moon system.Edited by 2gud, : No reason given.Edited by 2gud, : Re-phrased certain sentences

Please let me know where you are right and where I am wrong.I don't have a problem in accepting if I am wrong I thought none of us are Prophets (messengers of God whose words are infallible) and we are discussing a scientific topic!

Thanks for letting me know it is a joke.I was addressing the first post of this topic - in which the thread starter no where asked "why doesn't the moon orbit the sun?"His question of why doesn't moon get pulled away from Earth-Moon system into a separate orbit of its own around the Sun is still valid.And I answered it with the exact scientific explanation.If you are more interested in understanding under what conditions a planet can have a satellite, read about "Roche limit" and "Roche Lobe" in particulare. The conept of Roch Lobe is what which I explained in so many words.Edited by 2gud, : Rephrased certain sentences

Though the conclusion that the kid drew can be quite easily proved false, but still I am impressed that a kid asked a question (what is his age?) like "why don't rocks on earth orbit mountains". It is a interesting question indicating a inquisitive mind.Sometimes we tend to ask some questions whose answers are beyond our conception at that point of time. It happened with me several times. I distinctly remember asking my physics teacher in 7th standard, that why all the planets have to rotate in more or less in the same plane, why can't their orbits be tilted at angles like 20/30 degrees to each other, and why does only pluto have such orbit, the teacher couldn't give me an answer. But he was nice to have referred the question to a professor who could answer the question.