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I know that Earths gravity pulls down the Moon towards the Earths center and Moon is falling on Earth, but because of its change in velocity it never fall on Earth but orbits around Earth.

Now I don't understand why the Moon can not change its orbit around the Earth to some other planets. As a planet comes near to Moon where the new planets gravity is more than Earths gravity. And the Same situation's why not applying on other planets like Mars and Earth when they are Perihelion point, change it's orbits and orbiting each other or one orbit to another.

Communisty
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Imran Khan
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3 Answers3

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The higher the mass/distance-between-objects-squared the higher their mutual influence under gravity.

In solar system (excluding the earth) the planet having bigger mass/distance-to-moon-squared is Jupiter. So, let’s consider Jupiter-to-Moon Vs Earth-to-Moon influence only.

The closest distance between earth (moon) and Júpiter is $5.9×10^8 km$. Considering also

$m_{earth}=6×10^{24} kg$;

$m_{jupiter}=1.9×10^{27} kg$;

$d_{earth-moon}=3.8×10^{5} km$;

$d_{jupiter-moon}=6.3×10^{8} km$;

Now, if α is the ratio between Earth and Jupiter’s gravitational influence, then

$$\rm α= \frac{M_{earth}}{M_{jupiter}}(\frac{d_{jupiter-moon}}{d_{earth-moon}})^2=7.4×10^{3}$$

Therefore, Earth exerts a force ten thousands times stronger than any other planet into Moon, so we are not going to lose her soon (though we may lose her as Lawrence B. Crowell said).

PS: Every object in solar system (I’m avoiding using the universe), do act on others making slight changes in orbit, speed, velocity depending on how strong the interaction is, as a matter of fact, Neptune (and then Pluto) was predicted before observation just because of the anomalies it caused in the obit of Uranus.

J. Manuel
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In effect this will happen in a way at least in theory. The orbital angular momentum of the Earth's rotation is being transferred to the moon. This is due to tidal interaction between the Earth and the moon. The orbit of the moon is being nudged outwards. Think of a line from the center of the sun through the Earth. The moon crosses this line twice in its orbit around the Earth. However, once the moon is sufficiently far out that its velocity is equal or lower than this line then it is effectively free of the Earth.

This will happen in 50 billion years, which means it will be interrupted by the sun in its red giant phase where it will likely swallow up Earth and moon.

There are these libration points where centripetal forces and gravitation of many body systems balance. These Lagrange points can be stable or saddle points that are unstable in one direction and stable in the other. In the solar system the planets have their Lagrange points which perburb each other as they come close. It is then possible for a mass to hop from one to the other and move around the solar system this way. This is the interplanetary transport network which has been proposed as a way to get spaceprobes to perform long term explorations. It is possible that over a long period of time that trojan asteroids as Lagrange points might migrate around the solar system, and in the early solar system this may have involved larger bodies comparable to moons around some of the planets.

Lawrence B. Crowell
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I think it is because we are literally closer

World Walker
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