the one clock is simultaneous (in the above sense) with the same
position, of the pointers of the other clock, then identical "
settings " are always simultaneous (in the sense of the above
definition).


Notes

*) We suppose further, that, when three events A, B and C occur in
different places in such a manner that A is simultaneous with B and B
is simultaneous with C (simultaneous in the sense of the above
definition), then the criterion for the simultaneity of the pair of
events A, C is also satisfied. This assumption is a physical
hypothesis about the the of propagation of light: it must certainly be
fulfilled if we are to maintain the law of the constancy of the
velocity of light in vacuo.



THE RELATIVITY OF SIMULATNEITY


Up to now our considerations have been referred to a particular body
of reference, which we have styled a " railway embankment." We suppose
a very long train travelling along the rails with the constant
velocity v and in the direction indicated in Fig 1. People travelling
in this train will with a vantage view the train as a rigid
reference-body (co-ordinate system); they regard all events in

Fig. 01: file fig01.gif