Is it possible to give the setup of an experiment which tells you that your frame is moving at a constant velocity?

If yes, what can the experiment be?

  • $\begingroup$ No, see Galilean invariance $\endgroup$
    – lemon
    Commented Oct 20, 2017 at 14:08
  • $\begingroup$ Well, there is a disagreement between the question in the title and the question in the body. My off-hand approach to the question in the body is "Try juggling." but it does assume that you can juggle in the first place. $\endgroup$ Commented Oct 20, 2017 at 16:19
  • $\begingroup$ How will juggling help? $\endgroup$ Commented Oct 21, 2017 at 5:02
  • $\begingroup$ It will tell you if you are in an inertial (or nearly inertial) frame. Well, actually it will identify such frames on a large gravitating bodys, but that's a minor point for the time being. $\endgroup$ Commented Oct 22, 2017 at 3:26

1 Answer 1


Assuming we are talking about the standard physics situation where you are coasting through outer space in a spaceship with no windows, the answer is no, there is no experiment you could perform which would tell you what your velocity is. The mathematical and physical reasoning behind this can be found in texts dealing with special relativity.

  • $\begingroup$ Galileo wrote about this a few years before Einstein did... $\endgroup$ Commented Oct 22, 2017 at 3:27
  • $\begingroup$ agree, but einstein did the math which showed that it was in principle impossible to discern absolute motion- or so it seems to me. $\endgroup$ Commented Oct 25, 2017 at 6:19

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