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The Moon: Its Rotation and Bulging

written by: Melina Ann Collison • edited by: Kellie Hayden • updated: 8/2/2012

The Moon does rotate around our Earth. The cycle is 27.32 days. Why do people always think they see the same side of the moon if it rotates? Did the Moon always rotate at this speed? Why does the Moon have bulges? Learn everything you need to know about the Moon's rotation.

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    Does the moon rotate?

    Yes, the Moon does rotate. Not only does it rotate but the process happens at the same speed which it orbits around our Earth. Every 27.32 days the Moon completes a full circle around the planet Earth and a full circle on its own axis. Almost every moon in the solar system rotates and spins at the same rate with a few exceptions. These exceptions are due to asteroids and the forces which have an effect on the speed of the moons rotation have not had the appropriate length of time to even out the rotational periods.

    Full Moon By Luc Viatour 

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    Do I Always See the Same Face of The Moon?

    Author: Tomruen Yes, you do always see the same side of our Moon. This is because of how the Moon moves on its own axis. The Moon and the Earth both move at the same rotation. As the Moon travels around the planet Earth it is slowly rotating as well. These two rotations are perfectly in sync with each other. This is where the popular phrase “dark side of the Moon” comes from; since the Earth never sees one side of the Moon. However, while Earth has its view of the Moon the opposite side is basking in the glow of light from the sun. The Moon does have days and nights just like there are on Earth.

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    The Bulging Moon

    There are two bulges on either side of our Moon due to gravitational attraction. One bulge is on the side of the Moon nearest to the planet Earth and the other bulge is on the direct opposite side of the Moon furthest away from Earth. The Moon’s bulges move withPhoto By NASA  the gravitational pull. The pull is weaker on the side furthest away from Earth and stronger on the side closest. This process is similar to the water tides we have here on Earth.

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    Spinning Out of Control

    The Moon was formed around 4+ billion years ago and used to spin a lot faster. The rotation slowed down because the bulge in the Moon would always be in front of the gradational pull line with Earth and that process created torque which slowed things down. The torque was stopped being produced when the Moon slowed down to match the Earth’s orbital rate and the Moon’s bulge became in line with the planet. This rotation speed is another reason why we always see the same side of the Moon. The Moon does slightly shift from side to side during its circle around the Earth but only one side faces the planet at all times. Scientists say that the Moon is looked tidally to the planet Earth. When the Moon rotated faster than the Earth it presented all sides of itself to the planet.

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    References


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