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its not a pefect sphere, it has a bulge from the left over debris that formed into the moon...
The migration of the Moon away from the Earth is mainly due to the action of the Earth's tides.
The Moon is kept in orbit by the gravitational force that the Earth exerts on it, but the Moon also exerts a gravitational force on our planet and this causes the movement of the Earth's oceans to form a tidal bulge.
Due to the rotation of the Earth, this tidal bulge actually sits slightly ahead of the Moon. Some of the energy of the spinning Earth gets transferred to the tidal bulge via friction.
This drives the bulge forward, keeping it ahead of the Moon. The tidal bulge feeds a small amount of energy into the Moon, pushing it into a higher orbit like the faster, outside lanes of a test track.
But the energy gained as the Moon is pushed higher is balanced by a reduction in the energy of its motion - so an acceleration provided by the Earth's tides is actually slowing the Moon down.
