Printer Friendly

Wait a second!

New Year's 2006 will have to wait. An extra second--called a leap second--will be added to the last day of 2005.

For thousands of years, people have defined time by Earth's rotation on its axis: A complete rotation around this imaginary line marks one day.

But Earth isn't spinning as fast as it used to, says Tom O'Brian, chief of the time and frequency division of the National Institute of Standards and Technology. One slowing factor is the moon's gravity. Its pulling force creates a bulge on the part of Earth's surface that's closest to the moon. As Earth spins, the moon continues to tug on that bulge. The result? A slight slowing of Earth's rotation, and a tiny lengthening of each day. "For example, a day is about one or two thousandths of a second longer now than it was in 1905," O'Brian explains.

Each time those added milliseconds approach a full second, scientists add a leap second to atomic clocks. These precise clocks are used as a standard for the world's time.
COPYRIGHT 2005 Scholastic, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

 
Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Earth's rotation
Author:Jakubiak, David
Publication:Science World
Article Type:Brief Article
Geographic Code:1USA
Date:Dec 12, 2005
Words:174
Previous Article:Sound off.
Next Article:Pet power.
Topics:


Related Articles
Plugging holes with stratospheric winds.
Dragging frames of relativity.
Opening doors to the core, and more.
Wherefore the world's wobble?
Oracle bone shows a once-shorter day.
Earth's core out of kilter.
Reservoirs speed up Earth's spin.
Putting a new spin on Earth's core.
Superfluid gyro detects Earth's spin.
Solving one mystery of polar wander.

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters