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Unstrange Phenomena

01 March 2010

Chilean Earthquake Shortened Earths Day




From Denny: This is a fact few of us thought about when we first heard the news of the 8.8 earthquake in Chile. It really does make us wonder about the idea of the exponential curve in relation to a longer period of time how these incidences will add up to effect the planet. What am I talking about? The Earth's day is now just a small amount shorter.

Richard Gross, and another scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, put the pencil to the math. They calculated this recent high magnitude earthquake has now shortened the day by 1.26 microseconds. In case you forgot, a microsecond is one-millionth of a second. The length of a day is the time it takes for Earth to complete one rotation: 86,400 seconds or 24 hours.

OK, so how did this earthquake accomplish this feat of shortening Earth's day? It caused the Earth to rotate faster by nudging some of its mass closer to the planet's axis. Reminds you of one of those Olympic skaters in a spin where they pull up their arms to increase the speed of the spin.

The opposite can happen too. An earthquake "can slow the rotation and lengthen the day - if it redistributes mass away from that axis," Gross said.

Can this small change be permanent? According to Gross the answer is yes. He also commented that a series of high magnitude earthquakes like this one could possible add up to make the day shorter "but these changes are very, very small."

How small are these changes? There are so small that scientists are not able to record them directly. You would be surprised how much of science is not direct but rather indirect observation and recording. Gross also stated that true observations of the length of the day are accurate to five-millionths of a second. What about his estimate? His estimate about the Chilean quake's effect is just a quarter of that span of time.


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