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I always visualized that the tidal locking to be sort of like meshed gears, such that the one revolution around itself is same as a rotation around the star/planet if its a satellite.

But that shouldn't affect the day/night in this case right? Since we are talking about planets not satellites of planets and they are light sources not just reflecting light from the star. Can you please correct where I am wrong?



Tidal locking means that the denser side of the lighter body always faces the heavier body, and the less-dense side of the lighter body already faces away from the heavier one.

The moon is tidally locked to the Earth, which is why it has a dark side.


There is no dark side in the moon.

There is a far side.


You're right, but I'm pretty sure that "The dark side of the Moon" is a proper name at this point.

It's dark like the darknet is dark... Occluded.


So the Apollo "earthrise" photos are just "earth"?


No; they weren't taken from the moon; they were taken from the Apollo 8 spacecraft, which was orbiting, so the Earth did in fact 'rise'.


Yes, Earth does not move significantly on the moon sky, if i remember right. It does rotate though.

Edit: Archgoon is right, the photos were taken from the orbiting module, so a rise happened.


It follows from "one revolution around itself is same as a rotation around the star" that a planet tidally locked to its star presents the same face to the star at all times, so you have a 'Day' side and a 'Night' side. Neither side of which is likely to be particularly life friendly. Perhaps there might be some 'twilight zone' that could be though...




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