', the propagation of light takes place according to this equation. We thus see that the velocity of transmission relative to the reference-body
' is also equal to
. The same result is obtained for rays of light advancing in any other direction whatsoever. Of course this is not surprising, since the equations of the Lorentz transformation were derived conformably to this point of view.
[11]A simple derivation of the Lorentz transformation is given in Appendix I.
XII
THE BEHAVIOUR OF MEASURING-RODS AND CLOCKS IN MOTION
I PLACE a metre-rod in the
