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Is each day is really shorter?

Dear Control Engineering: I heard something about the recent earthquake in Chile affecting the earth’s rotation. What’s that about?

March 06, 2010


Dear Control Engineering: I heard something about the recent earthquake in Chile affecting the earth’s rotation. What’s that about?As strange as it sounds, NASA believes that the movement of the tectonic plates of the earth that caused the earthquake in Chile on February 27 has shifted the position of the earth’s axis and its rotation has speeded up. The Jet Propulsion Laboratory has reported that its calculations suggest that the earth’s figure axis, which is the axis on which our planet’s mass balances, shifted by about 3 inches during the earthquake. With that shift, the earth’s diameter has actually gotten smaller. This change has caused the earth’s rotation to speed up causing a day to be slightly shorter. The emphasis is on slightly, since the difference is a whopping 1.26 microseconds.

The JPL came to a similar conclusion after the big earthquake in Sumatra in 2004. Most of the news surrounding that quake was about the resulting Tsunami, but it was caused by a massive shift on the sea floor. The change in a day’s length was much more dramatic following that event at 2.68 microseconds. Such changes can’t really be measured, but they can be calculated.

So, feel free to leave work early.

Posted by Ask Control Engineering on March 6, 2010