> If so how can you claim that the ship is at rest? The ship is at rest with respect to its own reference frame. > So do you deny that the earth is moving? I

> If so how can you claim that the ship is at rest? The ship is at rest with respect to its own reference frame. > So do you deny that the earth is moving? I assume not. The earth is at rest with respect to its own reference frame. It is moving with respect to other things, such as the sun, or the center of the galaxy. Motion and rest are relative. This is the key concept, and I don't understand why you're having such trouble with it.