The Earth seems to be a pretty good inertial system, because on the ground, you leave something, it stays there.

地球看上去是个不错的惯性系,因为什么东西放在地上,都会保持静止

耶鲁公开课 - 基础物理课程节选

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

耶鲁公开课 - 基础物理课程节选