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Why Does the Earth Rotate?

Though we can't feel it, planet Earth is constantly spinning beneath our feet. The Earth rotates on its axis, an imaginary line that runs through the center of the planet, through the North and South poles. The axis is the Earth's center of gravity, around which it rotates. Though spinning at 1,000 miles per hour, the Earth takes 24 hours to make a complete rotation. Scientists continue to work towards an understanding of why the Earth spins and continues to rotate on its axis.

How Earth Began Its Rotation
- Most scientists speculate that a shock wave from a supernova went through a cloud of cold hydrogen, forming a solar nebula. The momentum caused the nebula to spin into a planetary disk. When the solar system was being formed, it is likely that collisions of these clouds contributed to the tilt and rotation of the Earth as we know it today.
Why the Earth Keeps Spinning
- The laws of physics state that an object that is in motion will remain so until an outside force acts upon the object. The Earth keeps spinning because there is nothing to stop it, as space is a vacuum. Not even earthquakes have been able to keep the earth from its rotation.
The Earth's Spin is Slowing
- While it is unlikely that any outside force will act on the Earth to stop its spin, the rotation of the planet is slowing. This is caused by tidal friction created by the oceans' movement. Tidal friction is caused by the gravitational pull of the moon. The result of tidal friction is that over the course of a century, the length of day can be extended by a few moments.
The Influence of the Earth's Spin
- The axis that the Earth is situated on is not a vertical line, but is at a 23.5 degree tilt. This angle is what causes the different climates and seasons at varying times around the globe. In addition, human beings mark time by the Earth's rotation. One full spin encompasses the measure of a day.

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