Friday, 29 January 2010

Why do we always see the same side of the Moon?...

This is due to the effect known as 'Gravitational Locking'. The Earth's gravitational field slowed the Moon's spin over time and now the Moon spins about its axis at a rate such that the time to rotate once on its axis is exactly equal to the time it takes to go round the Earth. The diagram (click on the figure to see it clearly) explains how this results in effectively the same side of the Moon facing the earth all the time.
Gravitational Locking is observed in the case of other planets as well whose satellite moons are locked in the same way as the Moon is locked to the Earth.

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