Synchronous Rotation

Synchronous rotation is an astronomical term that is used to describe a celestial body orbiting another celestial body in a manner such that the orbiting body takes as long to rotate on its axis as it does to make one orbit. Therefore, it always keeps the same hemisphere pointed at the celestial body it orbits around.

Another explanation for a synchronous rotation is that a celestial body may appear locked in the sky from a surface of another celestial body where it is observed. The moon is in synchronous rotation with the Earth, thereby it appears locked in the sky when we look at it. Most moons in the solar system are known to be of synchronous rotation with the planets their orbit due to what is called as tidal locking.

The moon’s synchronous rotation was said not be like this during its earlier years of existence, however, the Earth’s gravitational pull made the moon’s rotational speed slower. Therefore, some 3-4 billion years ago, the moon was rotating its axis and revolving around the earth in a faster pace than what its present speed. Today, the moon rotates on its axis for 27 days, 7 hours and 43 minutes while it revolves around the earth. That is why we always see the same side of the moon facing us. Another factor influencing moon’s synchronous rotation is the asymmetrical distribution of its mass, allowing Earth’s gravity to only keep one lunar hemisphere permanently facing the earth.

In thousands of years to come, the moon is predicted to be closer than its present distance of 384,403 kilometers from the earth. At that time, the moon’s synchronous rotation may be faster than its present speed and during those times the tidal forces between the earth and the moon may cause some alterations in current sea levels.

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