很多人认为地球绕太阳的轨道是完美的圆形，就像手在一块制作精良的手表上移动那样平滑、有规则，但事实并非如此。

A lot of people think of earth's orbit around the sun as being perfectly circular, as smooth and as regular as, say, the way that hands move on a well-made watch, but it just doesn't work that way.

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手表上的三条轨道可以在表面旋转来表示时间，而秒圈则会每时每刻都在变化。

Those three line are rotating around the watch and show the time, while the seconds line is going around all the time.

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