Massive Chile earthquake may have clipped fraction of second off Earth's day

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Massive Chile earthquake may have clipped fraction of second off Earth's day

1 hour, 26 minutes ago

By Malcolm Ritter, The Associated Press

NEW YORK - Earth's days may have gotten a little bit shorter since the massive

earthquake in Chile, but don't feel bad if you haven't noticed.

The difference would be only about one-millionth of a second.

Gross, a scientist at NASA's Jet Propulsion Laboratory in Pasadena,

California, and colleagues calculated that Saturday's quake shortened the day by

1.26 microseconds. A microsecond is one-millionth of a second.

The length of a day is the time it takes for the planet to complete one rotation

- 86,400 seconds or 24 hours.

An earthquake can make Earth rotate faster by nudging some of its mass closer to

the planet's axis, just as ice skaters can speed up their spins by pulling in

their arms. Conversely, a quake can slow the rotation and lengthen the day if it

redistributes mass away from that axis, Gross said Tuesday.

Gross said the calculated changes in length of the day are permanent. So a bunch

of big quakes could add up to make the day shorter, " but these changes are very,

very small. "

So small, in fact, that scientists can't record them directly. Gross said actual

observations of the length of the day are accurate to five-millionths of a

second. His estimate of the effect of the Chile quake is only a quarter of that

span.

" I'll certainly look at the observations when they come in, " Gross said, but " I

doubt I'll see anything. "

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