This comparability of time-measurements will be achieved by another method which depends on the fact that relative velocity is equal and opposite. The explanation of this method must be reserved for the next chapter.
[7]This definition of congruence is given by Profs. E. B. Wilson and G. N. Lewis in their valuable memoir, 'The Space-Time Manifold of Relativity,' Proc. of the Amer. Acad. of Arts and Sciences, vol. XLVIII, 1912.
[CHAPTER XIII]
MOTION
[49. Analytic Geometry]. 49.1 Consider any time-system
: we will term the space of this time-system '
-space' and its moments '
-moments'; also the points and straight lines of