Chile quake may have tipped Earth's axis

http://www.cnn.com/2010/WORLD/americas/03/02/chile.quake/index.html?hpt=T1

March 2, 2010 7:45 p.m. EST

(CNN) -- The massive earthquake that struck Chile on Saturday may have shifted Earth's axis and created shorter days, scientists at NASA say.

The change is negligible, but permanent: Each day should be 1.26 microseconds shorter, according to preliminary calculations. A microsecond is one-millionth of a second.

A large quake shifts massive amounts of rock and alters the distribution of mass on the planet.

When that distribution changes, it changes the rate at which the planet rotates. And the rotation rate determines the length of a day.

"Any worldly event that involves the movement of mass affects the Earth's rotation," Benjamin Fong Chao, of NASA's Goddard Space Flight Center in Greenbelt, Maryland, said while explaining the phenomenon in 2005.

Scientists use the analogy of a skater. When he pulls in his arms, he spins faster.

That's because pulling in his arms changes the distribution of the skater's mass and therefore the speed of his rotation.

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