Looking up at the silvery orb of the Moon, you might recognize familiar shadows and shapes on its face from one night to the next. You see the same view of the Moon our early ancestors did as it lighted their way after sundown.
Only one side of the spherical Moon is ever visible from Earth — it wasn’t until 1959 when the Soviet Spacecraft Luna 3 orbited the Moon and sent pictures home that human beings were able to see the “far side” of the Moon for the first time.
A phenomenon called tidal locking is responsible for the consistent view. The Earth and its Moon are in close proximity and thus exert significant gravitational forces on each other. These tidal forces slow the rotations of both bodies. They locked the Moon’s rotation in sync with its orbital period relatively soon after it formed — as a product of a collision between a Mars-sized object and the proto-Earth, 100 million years after the solar system coalesced.