Earth & Space
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Planets, weather, oceans and the sky above them.
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Why there are two high tides a day: the Moon pulls the near sea harder and the far sea softer
The sea rises twice a day, not once, and the second high tide happens on the side of the Earth facing away from the Moon. Why? The Moon pulls the near ocean a…
Why the Moon changes shape: always half lit, and only part of it faces you
Ask why the Moon changes shape and most people blame the Earth's shadow. It is a natural guess, and it is wrong: the Moon is half lit by the Sun all the time…
Why the Moon always shows us the same face: tidal locking
The Moon does spin. It turns exactly once for every trip around the Earth, so the same face always points our way. Walk around a chair while always facing it…
Why we only ever see one side of the Moon
The Moon always shows us the same face, so it's easy to assume it doesn't spin. It does. It turns exactly once for every orbit, about every 27.3 days, so the…