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The massive earthquake that struck Chile in February 2010 might have shortened Earth's day by 1.26 microseconds, according to calculations by a NASA scientist. An EarthSky Facebook friend asked us how. And the answer is for the day to get shorter, Earth's rotation¹ has to speed up.

根据美国航天航空局科学家的计算，2010年2月的智利大地震使地球一天缩短1.26微妙。EarthSky的Facebook好友询问我们这一现象是如何发生的。答案即：地球自转加快了，一天的时间才会变短。

Richard Gross:  The Earth's rotation changes all the time. It speeds up and it slows down and it wobbles as it rotates. These changes are caused by anything that moves mass around on the Earth.

理查德·格罗斯：地球的自转是时刻改变的，时而加速，时而减速，在旋转的时候还会摆动。地表任何剧烈的运动都会引发这些变化。

That's Richard Gross, of NASA's Jet Propulsion Laboratory. He is the scientist who performed the calculations.

这位是NASA喷气推进实验室的理查德·格罗斯，是完成该计算的科学家。

Richard Gross:  This is just like a spinning ice skater who will spin faster as she brings her arms closer to her body. The net result of the mass motion that was everywhere within the earth was to rearrange the Earth's mass in such a manner that it brought it a bit closer to the Earth's rotation axis² causing the Earth to rotate a bit faster and the length of the day to be a bit shorter.

理查德·格罗斯：花样滑冰者在旋转时收回手臂就会转的更快，这其实和地球旋转的原理是类似的。地球内部各处地块运动的最终结果是使地球质量重新分布，向地球旋转轴靠近一点点，加快地球旋转，一天的长度也就缩短一点。

Dr. Gross said there won't be any practical consequences from the shortening of our day. In fact, winds and oceans currents have an even bigger effect on the length of the day than this earthquake did. In the end, the change is too small to detect even with the most sophisticated instruments.

格罗斯博士说一天时间的缩短不会带来任何实际后果。事实上，相对地震，季风和洋流对一天时间长短的影响更大。最终，这种变化小到最精密的仪器都检测不到。