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.
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.
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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