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Why is earth's moon spherical?

1 Answer
Sep 6, 2015


Actually, the moon isn't a sphere.


It's an oblate spheroid — a sort of "squashed sphere" in which the equatorial radius is greater than the polar radius.


The Moon is nearly spherical because of gravity.

Gravity is a force that points inwards from all directions towards a centre.

Small asteroids and moons can be non-spherical, but after they reach about 600 km in diameter, the force of their gravity can "break" the rock from which they are made.

All the bumps are pulled down, and they become more spherical.

But, because it’s rotating, the Moon flattens out slightly.

The equatorial diameter of the Moon is 3 476.28 km. And the polar diameter of the Moon is 3 471.94 km.

So, the Moon’s diameter from side to side is 4.34 km more than its diameter from pole to pole.