Because the moon takes exactly precisely the same time to rotate once on its axis as it takes to revolve once in its orbit around the Earth.
The rotational period of the moon is equal to one revolution around Earth. ;
The same side of the Moon always faces the Earth due to a phenomenon called synchronous rotation, where the Moon rotates on its axis in the same time it takes to orbit the Earth. This is caused by the Earth's gravitational forces acting on the Moon. As a result, the near side of the Moon is always visible from Earth while the far side remains hidden.
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