If I am an inertial observer, another person moving relative to me at constant velocity will also be an inertial observer.

如果我是惯性观察者,那另一个相对于我做匀速运动的人,也是一个惯性观察者

耶鲁公开课 - 基础物理课程节选

But things which were at rest will move at a constant velocity, opposite of the velocity that you have relative to me.

这些静止的东西都在匀速运动,方向正好跟你相对我运动的速度方向相反

耶鲁公开课 - 基础物理课程节选

There's infinite number of them, but they're all moving relative to each other at constant velocity.

有无数个惯性观察者,但是他们都在相对于彼此,做匀速运动

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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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In particular, the things that I say are at rest, you will say are moving backwards at the velocity that you have relative to me.

特别是那些在我看来是静止的物体,在你看来却在后退,后退的速度等于我们之间的相对速度

耶鲁公开课 - 基础物理课程节选