If you think the sun might be setting a microsecond or two earlier tonight, it’s not your imagination. Rather, it would be your supernaturally honed senses. CNN reports that the magnitude-8.8 earthquake that struck Chile last week may have affected the length of the Earth’s days. According to preliminary calculations, each day may be 1.26 microseconds shorter.
But don’t set your clocks back just yet. A microsecond is one-millionth of a second and not perceivable to the human senses. The discovery is the work of Richard Gross, a geophysicist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Goss used a computer model to determine how the massive Feb. 27 Chilean earthquake may have affected the Earth. Apparently, the tectonic event shifted the Earth’s axis, or the way it is balanced. Via NASA, Gross revealed that the earthquake should have moved Earth's figure axis by 2.7 milliarcseconds. This is just about 8 centimeters, or 3 inches.
Scientists liken this event to the moves of a figure skater. When a figure skater pulls in her arms, she spins more quickly. The axis shift has redistributed the planet's mass — therefore, it is spinning more quickly, albeit at a non-perceptible rate.
This is not the first the time Earth has shifted as the result of a major global event. The length of a day last changed in 2004, when the magnitude-9.1 Sumatran quake shortened it by 6.8 microseconds. Benjamin Fong Chao of NASA's Goddard Space Flight Center in Greenbelt, Md., explained the process in 2005. As he told CNN, "Any worldly event that involves the movement of mass affects the Earth's rotation.”
Last week’s Chilean earthquake shortened the Earth’s spin, even though it was not as powerful as the 2004 Indian Ocean quake. Experts report that the Chilean quake was located in Earth's mid-latitudes, which makes it more effective in shifting Earth's axis. This fault also dips into Earth at a slightly steeper angle than does the fault responsible for the Sumatra event.
Will this new time change stick? Gross says that data on the Chilean quake is still being refined, so his calculations may change.