An observer in a closed room cannot tell which of the following is true: Objects are falling to the floor because the room is resting on the surface of the Earth and the objects are being pulled down by gravity.
一个在封闭房间中的观察者无法区分下列现象哪一个是正确的： 物体会掉到地上是因为这个房间处于地球表面，物体被地球的引力拉到地上。