英語(yǔ)時(shí)差：讓地球轉(zhuǎn)起來(lái)（下）

What’s true for skaters is also true for planets. Our Earth doesn’t have arms, but it does have a lot of oceans, which tend to bulge out at the equator. This weight distribution is like a skater with arms out, spinning slowly. In the past century, however, we’ve changed the way Earth’s water is distributed. By making reservoirs, we’ve effectively moved some ten trillion tons of water closer to the poles in the last forty years. Closer to the poles means closer to the axis of rotation–like a skater drawing her arms in, this has increased our Earth’s rotation. It’s an extremely small—but still measurable–amount. Reservoirs have made each day eight millionths of a second faster than it was forty years ago!