天文学家在距离地球不远处发现一颗小行星，它与地球在同一轨道上围绕太阳运行。

Astronomers have detected an asteroid not far from Earth, moving in the same orbit around the Sun.

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我喜欢设想一艘在轨道上运行的艘宇宙飞船如何利用这种现象。

I like to imagine how a spaceship might be able to take advantage of this phenomenon, by orbiting it.

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无论你是谁，生活在哪里，挣多少钱，受过多么良好的教育，生活的道路都是一定的，就像火车在轨道上运行一样。

Regardless of who you are, where you live, how much you make, or even your education, your life is on a certain path - similar to a train on a track.

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If you escape the pull of gravity, your spaceship will be off, won't be orbiting the Earth.

如果你完全脱离重力,太空船早就飞得没影了,而不是在轨道上运行

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And orbiting around this is a lone electron out at some distance r.

有一个单电子,在环原子核的轨道上运行。

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I am going to say if that electron is to stay in its orbit, that is to say it doesn't flee the atom, it doesn't collapse under the nucleus then the sum of the forces on the electron must be zero No net force. And so that will be the sum of a dynamic force plus an electrostatic.

如果电子会保持在它的轨道上运行,既不脱离原子的话，它就不会由于原子核对它的吸引力而被瓦解掉,电子所受的合力一定为零,由于没有合力,所以电子所受力为动态力和静电力的总和。

麻省理工公开课 - 固态化学导论课程节选