vanish together. This proves Einstein's theorem on the invariance of the velocity
, so far as concerns the sufficiency of the Lorentzian formulae to produce that result.
[CHAPTER IV]
CONGRUENCE
[11. Simultaneity]. 11.1 Einstein analysed the ideas of time-order and of simultaneity. Primarily (according to his analysis) time-order only refers to the succession of events at a given place. Accordingly each given place has its own time-order. But these time-orders are not independent in the system of nature, and their correlation is known to us by means of physical measurements. Now ultimately all physical measurement depends upon coincidence in time and place. If
and
be two places, the time-orders