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Chile earthquake made days shorter: Nasa
Published on 3 Mar. 2010 11:52 PM IST
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The Chilean earthquake has shortened the length of the day by making the Earth rotate faster, according to Nasa scientists. But you might not have noticed, as it was only by about one-millionth of a second. Richard Gross has revealed the disaster, which has killed at least 795 people, shortened the length of a day by about 1.26 microseconds. A microsecond is one millionth of a second. Perhaps more impressive is how much the 8.8 magnitude quake shifted Earth’s axis. Dr Gross, from Nasa’s Jet Propulsion Laboratory, calculated the quake should have moved Earth’s figure axis (the axis about which Earth’s mass is balanced) by about three inches. Earth’s figure axis is not the same as its north-south axis; they are offset by about 30 feet. By comparison, Dr Gross said the Sumatran earthquake from 2004 should have shortened the length of day by 6.8 microseconds and shifted Earth’s axis by 2.76inches. It didn’t shift the Earth’s axis as far because the earthquake was located nearer the equator. Dr Gross said the calculated changes in the length of a day are permanent. But he added: ‘These changes are very, very small.’ 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, Dr Gross said.

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