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If this skater extended her arms as far away from her body as she could, she would spin more slowly. The Earth would spin more slowly if molecules of the atmosphere clustered near the equator.
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Windows to the Universe

Can Earthís Spin Be Changed by Wind?
News story originally written on March 19, 2003

Our atmosphere changes all the time. Winds and air pressure change over days, weeks, and years. These changes affect our weather. Now scientists say that they also affect how the Earth spins around and around.

Each day the Earth spins around in one circle. Between the time that you woke up this morning and time that you will wake up tomorrow, the Earth will have made one more turn around. If the Earth turned faster, days would be shorter. If the Earth turned more slowly, days would be longer. So, if wind can affect the speed of the spinning Earth, then the length of days could change!

How does the air around us affect the spin of our planet? Earth is spinning like a skater spins on the ice. When a skater moves his or her arms out, there is weight far from the middle of the skaterís body. This causes the skater to turn slower. The spinning Earth works in the same way! When there is high atmospheric pressure at the equator, the weight of tons of air molecules is far from the middle of the Earth. Just like the skaterís arms, the air molecules cause Earth to turn more slowly.

A team of scientists figured out what was happening by comparing measurements from the atmosphere with measurements of how the Earth spins. They found that the changes to how Earth spins can even cause a small fraction of a second of change in the length of a day. (So if you feel like itís been a very long day, you may be right!)

Last modified July 31, 2003 by Jennifer Bergman.

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