If you want to make sure you get enough sleep on Tuesday night, you might have to get to bed earlier. You don’t have to adjust your schedule by much: about 1.26 millionths of a second ought to do it. According to a NASA scientist’s computer modeling, that’s how much an Earth day should have been shortened by the subterranean upheaval that triggered the Feb. 27 earthquake in Chile. Some basic physics explains why. — in the case of the Chile earthquake, by about three inches. The law of conservation of angular momentum, however, requires that even under these exigent circumstances, the Earth’s angular momentum stays constant, which means the planet must step on the gas to accommodate shifting mass. The same thing happened in 2004 with the 9.1 Sumatran earthquake that triggered the tsunami. That earthquake should have shifted the Earth’s figure axis by 2.76 inches and shortened its day by 6.8 millionths of a second, according to computer models.
If the physics seems a bit arcane, consider that you probably spent much of the past two weeks seeing the angular-momentum principle in action — at least if you watched the Olympics. Earthquakes change the Earth’s rotation the same way a twirling figure skater changes hers — by extending or tucking her arms in, for instance, to slow down or speed up accordingly. The only difference is that the skater does so decidedly more elegantly.
Watch TIME’s video “Harsh Lessons for Chile and Haiti from Peru.”
See the best pictures of 2009.
