Einstein (1905)addressed the question of distant simultaneity by writing (as quoted in
translation by Jammer, p. 110), ‘‘But it is not possible to compare the time of an event at A
with one at B without a further stipulation; thus far we have only defined an ‘A-time’ and a
‘B-time’ but not a ‘time’ common to A and B. The latter can now be determined by
establishing by definition that the ‘time’ needed for the light to travel from A to B is equal
to the ‘time’ it needs to travel from B to A.’’ We thus see that standard simultaneity is
equivalent to saying that the one-way velocity of light is isotropic.