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by fspeech
2731 days ago
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The balance is between Moon and Earth gravity. However it is more subtle than that at L2 as both gravitational forces are in the same direction so they don't apparently cancel. The way to see it is to realize that L2 is relatively stationary to the Moon but not the Earth. As the L2 point is farther away than the Moon but has the same angular velocity as the Moon, Earth gravity alone is not able to keep any object at the L2 in synchrony with the Moon. One may want to recall that Earth gravity is just right for the Moon in its orbit so any satellite further away will have a longer orbital period than the Moon. The Moon gravity therefore supplies the additional force needed to keep an object at L2 orbiting the Earth in synchrony with the Moon. This balance (Earth gravity + Moon gravity = centrifugal force) determines the location of L2. |
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