Meridian Star

New Today

July 17, 2013

Stutters in Earth's spin changed length of days slightly

Three times in the past decade, the Earth's spin has missed a beat as seemingly random blips cause days to temporarily stretch and shrink. They have emerged from the clearest-ever view of how long a day is.

Earth's rotations fluctuate as the oceans and the atmosphere push and tug on the spinning planet. But these small daily variations hide longer-term patterns.

Richard Holme of the University of Liverpool looked at 50 years of GPS and astronomical data to see how day length varied during that time. His analysis highlighted a well-known cycle of slow changes at the Earth's core, which lengthen days by a few milliseconds over roughly a decade, then shorten them again.

There's also a 5.9-year cycle, due to persistent friction between the Earth's fluid outer core and its surrounding mantle, a wobble that changes day length by fractions of milliseconds a year.

When Holme stripped away both of these regular cycles, though, sudden unexpected jumps in day length emerged from his calculations. Three times in recent years - in 2003, 2004 and 2007 - our planet's spin has stuttered. The jumps interrupted the longer-term changes by a fraction of a millisecond, and they lasted several months before going back to normal.

Satellite readings of the planet's magnetic field over the past 20 years show that the field also undergoes sudden jerks, and Holme found that they coincide with the jumps in the Earth's spin. He says the sudden changes probably occur when a patch of molten outer core temporarily sticks to the mantle, causing a steep change in angular velocity.



 

1
Text Only
New Today
Biz Marquee
New Today
Poll

People are carrying less credit card debt in the wake of the Great Recession. Have you changed your credit card use?

Yes
No
     View Results
Facebook
Facebook
Twitter Updates
Follow us on twitter
AP Video
Raw: Families Travel to Taiwan Plane Crash Site Arizona Execution Takes Almost Two Hours Gen. Odierno Discusses Ukraine, NATO at Forum Gaza Fighting Rages Amid Cease-Fire Efforts Mint Gives JFK Coin a Face-lift Creative Makeovers for Ugly Cellphone Towers Ariz. Inmate Dies 2 Hours After Execution Began Crash Kills Teen Pilot Seeking World Record LeBron James Sends Apology Treat to Neighbors Raw: Funeral for Man Who Died in NYPD Custody Migrants Back in Honduras After US Deports Israeli American Reservist Torn Over Return Raw: ISS Cargo Ship Launches in Kazakhstan Six Indicted in StubHub Hacking Scheme Former NTSB Official: FAA Ban 'prudent' EPA Gets Hip With Kardashian Tweet Bodies of MH17 Victims Arrive in the Netherlands Biden Decries Voting Restrictions in NAACP Talk Broncos Owner Steps Down Due to Alzheimer's US, UN Push Shuttle Diplomacy in Mideast
Hyperlocal Search
Premier Guide
Find a business

Walking Fingers
Maps, Menus, Store hours, Coupons, and more...
Premier Guide