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kichigai
Does anyone know why Mercury and our Moon do not spin?
enigma said:The Moon orbits the Earth.
You can tell because the side that faces the sun changes: phases of the Moon.
The Moon always has the same side facing us.
Therefore, the Moon rotates at the same rate which it orbits.
This phenomena is called 'tidal lock'.
Chronos said:The moon is mainly non-spheroid because of Earth's gravity.
employee #416 said:If I have not been mistaken, I thought we always saw one side of the moon at all times. We have never seen the other half of the moon. Wouldn't this imply that the moon does not spin? If the moon did spin, I'm sure it would be noticeable.
Uh, er, it just dawned on me that I repeated what you had already said :blush:Math Is Hard said:Well, yes. And doesn't this assist in the tidal locking phenomenon?
Welcome to Physics Forums Iron Sun 254!Iron Sun 254 said:It was once believed that Mercury did not spin and I've come across websites that still post this false information. Part of the reason for this misconception is the rotation period and orbital period are in phase so that Mercury rotates 3 times everytime it orbits the Sun twice. Even though it's rotating every other time it reaches the same point in an orbit it's facing the same direction.
Mercury has a slow rotation because it is located very close to the Sun. The gravitational pull of the Sun on Mercury is much stronger than the pull of Earth on its own moon. This tidal force causes Mercury to have a slower rotation as it is constantly being pulled towards the Sun.
The closer an object is to the Sun, the stronger the Sun's gravitational pull is on that object. This means that Mercury, being the closest planet to the Sun, experiences a greater tidal force that slows down its rotation.
The Moon's rotation is synchronized with its orbit around the Earth, meaning it takes the same amount of time for the Moon to rotate on its axis as it does to orbit around the Earth. This is due to the tidal forces exerted by the Earth on the Moon, causing the Moon's rotation to slow down and eventually become locked in this synchronized rotation.
Similar to Mercury, the Moon's distance from Earth also affects its rotation. The closer an object is to Earth, the stronger the Earth's gravitational pull on that object. This results in a stronger tidal force on the Moon, slowing down its rotation and causing it to become synchronized with its orbit around Earth.
Yes, it is possible for the rotation of Mercury and the Moon to change in the future. The tidal forces acting on these objects can change over time due to various factors, such as changes in their orbits or the gravitational forces of other celestial bodies. However, any changes in their rotation would likely occur over a long period of time and would be difficult to observe in a human lifetime.