The gravitational pull of the moon lifts up the ocean to cause tides. Well the Earth's gravitational pull is so strong on the moon that the heavier side of the moon always faces the Earth. This is called tidal locking. So the only way to ever see the far side of the moon is to go there. Humans have gone there before, but almost always during an Earth "full moon", which means the far side is unlit. We do have full images of the far side of the moon from remote probes, but the 21% of the far side that was lit had human eyes on it for the first time ever.

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grishka 6 hours ago | parent | next [-]

But why does this not happen to planets themselves in relation to the sun?

	▲	_moof 4 hours ago \| parent \| next [-]
		Moons get tidally locked because they're very close to their planet, so the planet's gravity is by far the strongest influence. The planets have much more complicated gravitational interactions because in addition to the Sun's gravity, they influence each other. So you end up with things like orbital resonances instead. A planet that's close to its star and far from other strong gravitational influences will tidally lock to the star.
	▲	anlsh 5 hours ago \| parent \| prev \| next [-]
		I think the explanation is wrong: wikipedia offers a completely different explanation https://en.wikipedia.org/wiki/Tidal_locking. Planets can become tidally locked to the sun- mercury is. Probably the timescale required for the other planets is just much longer EDIT: Apparently mercury isn't actually tidally locked to the sun, TIL
	▲	4 hours ago \| parent \| prev [-]
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CookieTonsure 11 hours ago | parent | prev [-]

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