If you're an inertial observer, then in your system of reference, objects left at rest will remain at rest.

如果你是惯性观察者,那么在你的参考系内,静止的物体会保持静止

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But if you go to outer space nowadays, you can find truly inertial frames of reference.

但如今,要是你到了外太空,你可以找到真正的惯性参考系

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So the Earth is an inertial frame of reference, if you go in a train relative to the Earth at constant velocity, you're also inertial.

所以,地球是一个惯性参考系,如果你坐在相对于地球匀速运动的火车里,你也处于惯性状态

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The point is that there are inertial frames of reference.

重点就是,惯性参考系是存在的

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You must know the Earth is not precisely inertial.

你们都知道,地球不是严格意义上的惯性参考系

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