The Clock Paradox

Science  27 Nov 1959:
Vol. 130, Issue 3387, pp. 1471-1472
DOI: 10.1126/science.130.3387.1471-a


In Minkowski space, a coordinate system can always be chosen so that the straight line (geodesic) joining two events (not on a null line) is either parallel to the time axis or parallel to the space axis. In either case the geodesic has maximum length (time dilatation and Lorentz contraction).