I have been reading Lieber's book "The Einstein Theory of Relativity" which describes the derivation of the Lorentz Transformations: archive.org/details/einsteintheoryof032414mbp -- see pages 39-56 bartleby.com/173/a1.html The entire derivation makes no sense, whatsoever. Why is it necessary to cover-up the whole problem? You cannot just state that there is a flash of light at the origin and proceed with the mathematics from there. What is the nature of the mysterious light flash at the origin which "stays" with the K and K' frames as they move? I mean, I thought physicists were precise...this is ridiculous. If somebody thinks they can step-by-step defend and explain either the original Einstein 1920 derivation, or Lieber's butchering of it, please step up.