For Dalespam: The difference between Lorentz and Einstein is that the transformation is only applicable to one frame and must be fully inverse for the moving frame. Lorentz transform into the moving frame but invert the calculation to arrive back at the stationary one. The transformation is applied the same in both frames for SR, because both frames actually are equivalent. The frames only "appear" equivalent to each observer in LET. In LET you convert from the "truth" of the stationary frame to the "illusion" of the moving frame whereas you convert from "truth" to "truth" in SR. It's not a difference in the math but in the application of it. There is absolutely no version of the twins paradox in LET because of this. In LET, the moving frame is length contracted and time dilated, but if you ever attempt to convert from the moving frame to the stationary then the moving frame sees the stationary frame as length dilated and time contracted. If you do not understand what I'm saying then you simply don't understand the genesis of LET which is perfectly understandable because it's a very esoteric subject. Most people don't spend their time learning old incorrect theories in detail. I do. Surely you understand that a child can show all their work for a word problem, solve every equation properly, but still solve the word problem improperly. This is the difference between the theories. Einstein showed that Lorentz had the right equations, solved them properly but failed the word problem. I'd be glad to help you understand this further if you're willing to learn about this old defunct theory. But your assumption that there is no difference between the theories just comes from the fact that nobody really cares anymore just like they don't care about the exact minutia in corpuscular theory, so some detail about the old theories get lost. I, however, enjoy looking into the process of errors that led us to where we are. If you are willing to have some patience, I will explain in detail -when I have a few minutes- why LET would assume that light would arrive at .466 but why SR knows it is .288 The difference is a single preferred frame of ether. The difference is that LET frames are not actually equal even though they appear to be to the observer inside them. In SR the frames are actually equivalent. In LET light appears constant in the moving frame because the changes to light's apparent speed (from being retarded by the ether) are balanced by changes to time such that they cannot be detected. (an illusion) In LET light governs time, in SR time governs light. As I said, if you wish, I can provide more detail and I believe you will see that what I'm saying makes sense if light traveled like sound does. We now know that it doesn't but it's entertaining to see that the Lorentz transformation will actually work for sound if you apply it as Lorentz initially did. (because he believed light was a mechanical wave in a medium) You only see that I'm applying the transformation incorrectly. You can see what Einstein saw about Lorentz, that I'm solving the word problem incorrectly (as Lorentz did), but wouldn't you also like to see what Lorentz saw?