Today , many people have been too much deeply in theory world and the others do not understand what they have said . We do not know what is right and what is wrong . People like to talk about the speed of light , but perhaps do not know what is a reference frame . I think we should talk about the speed of a body in the system , it is useless we talk the speed of the system relative to its native body or the speed of a remote body relative to another remote bady , such as the Earth relative to a fly or a car in china relative to another car in USA . Speed maybe divided into two kinds , kinetic speed and dynamic speed . We have found for long time that peope do not like to distinguish these two kinds of speed .
If Alice read all the posts in this thread, she would say curiouser and curiouser. I prefer weireder and weirder, with only a few rational statements.
Dynamic speed is with influence and kinetic speed is without it . Kinetic speed may be used only in calculating the diatance . Dynamic speed , such as a clock moving in the gravitationa field GAS of the Earth can make the clock work slowlier , but the speed of the Earth relative to the clock is kinetic speed and it can't make the Earth rotate slowlier . What is motion ? I think it is not distance changing . Motion is a man swims in water . Saying motion is distance changing , he is a mathematician , and saying motion is a man swims in water , he is an engineer . Engineers maybe greater physicists in future days .
