Why We Only See One Side of the Moon
Every person in history has looked at the same face of the Moon. This film explains why: how the Moon spins exactly once per orbit, how the tides that lift our seas also braked the Moon's spin until it locked, why the Moon is slowly drifting away and our days are getting longer, how a wobble lets us see 59% of the surface, and why the far side, first photographed in 1959, looks so different. A new study of Chang'e-6 samples offers one more explanation for that difference. Turn off the Moon's spin, line up the Sun and Moon for a spring tide, and spin down a young Moon yourself.
The locked face
Everyone who ever lived has seen the same side of the Moon.
It does spin
Exactly once for every trip around the Earth.
There is no dark side
The far side gets just as much sunlight.
A difference in pull
Why there are two high tides, not one.
Spring and neap tides
The Sun is stronger, but the Moon wins the tides.
How the lock happened
Earth raised tides in the Moon, and used them as a brake.
Longer days, a farther Moon
The same tides are still at work on Earth.
Locked worlds
Our Moon is the rule, not the exception.
The wobble
We actually see a little more than half.
The hidden half
No human saw the far side until 1959.
A lopsided Moon
The far side looks like a different world.
Why the difference?
Several ideas, no consensus yet.
The new proposal
What the far-side rocks suggest.
The locked face
The same force that moves the sea.
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