Shop Windows to the Universe

Our Glaciers: Then and Now activity kit helps you see the changes taking place in glaciers around the world. See all our activity kits and classroom activities.
If this skater extended her arms as far away from her body as she could, she would spin more slowly. Similarly, the Earth would spin more slowly if the molecules of the atmosphere were clustered in high pressure systems near the equator.
Click on image for full size
Windows to the Universe

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

Earth’s atmosphere is very complex and changes occur all the time. Winds and pressure patterns change over days, weeks, and years. Not only do those changes affect the weather, but also scientists have recently found evidence that they affect the rotation of the Earth as well, causing changes to the length of days. (So if you feel like today has been a very long day, you may be right!)

How does the air around us affect the spin of our planet? Concepts from physics, such as angular momentum, can help us understand how this happens. Angular momentum describes the spin of the Earth on its axis. Imagine that the spin of the Earth is like a skater spinning on the ice. When the skater moves his or her arms out, mass is moved far from the axis of rotation and the skater’s spin slows down. Similarly, when atmospheric pressure is high at the equator, increased mass is located far from Earth’s axis of rotation, and the spin slows.

Strong winds can also cause the Earth’s rotation to slow because, according to the laws of physics, the total amount of angular momentum must stay the same. “So if the atmosphere speeds up (stronger westerly winds) then the solid Earth must slow down (length-of-day increases),” says scientist David A. Salstein, who led the recent study to understand how the atmosphere affected Earth’s rotation.

Especially strong winds, like those related to El Nino, can cause small but measurable changes to Earth’s rotation. During El Nino, the rotation of the Earth may be slower because of the strong winds. Earth’s rotation does not slow very much, but it does make each day a fraction of a millisecond longer.

Salstein and his team looked at wind and pressure measurements from the National Weather Service. They used measurements of the Earth’s rotation from a variety of space-based observation systems such as GPS satellites and geodetic satellites. They compared the atmosphere data with the rotation data and found support for their hypothesis that the movements of air through our atmosphere affect Earth’s rotation!

Last modified July 31, 2003 by Jennifer Bergman.

Shop Windows to the Universe Science Store!

Our online store includes issues of NESTA's quarterly journal, The Earth Scientist, full of classroom activities on different topics in Earth and space science, as well as books on science education!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Wind

Wind is moving air. Warm air rises, and cool air comes in to take its place. This movement creates different pressures in the atmosphere which creates the winds around the globe. Since the Earth spins,...more

El Nino is Brewing Again

They've arranged for emergency evacuation. They've sealed off their garage, lining the walls of their house with sandbags. They even threw a "preparedness party" for the neighborhood. The O'Tooles of Southern...more

1999--A Year in Review...

It was another exciting and frustrating year for the space science program. It seemed that every step forward led to one backwards. Either way, NASA led the way to a great century of discovery. Unfortunately,...more

STS-95 Launch: "Let the wings of Discovery lift us on to the future."

The Space Shuttle Discovery lifted off from Kennedy Space Center at 2:19 p.m. EST, October 29th. The sky was clear and the weather was great as Discovery took 8 1/2 minutes to reach orbit for the Unitied...more

Moon Found Orbiting Asteroid

A moon was discovered orbiting the asteroid, Eugenia. This is only the second time in history that a satellite has been seen circling an asteroid. A special mirror allowed scientists to find the moon...more

U.S. is Fed Up with Russia

Will Russia ever put the service module for the International Space Station in space? NASA officials are demanding an answer from the Russian government. The necessary service module is currently waiting...more

More on Recent Coronal Mass Ejection

During a period of about two days in early May, 1998, the ACE spacecraft was immersed in plasma associated with a coronal mass ejection (CME). The SWICS instrument on ACE, which determines unambiguously...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF