If we get on a train and time the train’s travel over 1000 meters, we can calculate the train’s velocity; v = dx/dt But if our watch is running slow, we will measure incorrectly and think the train was going faster than it really was. v’ = dx/dt’ We know that when something moves very quickly, its clocks will run slower. So we know that we don’t have to have a broken watch for us to measure the wrong velocity. But the equation v’ = dx/dt’ requires that we make a choice that either our velocity measured, v’ is wrong or the length of the track has shortened, dx’, just because we were moving. Lorentz The Lorentz equations seem to have chosen to say that our distance has “really” shortened rather than say that we are merely experiencing the effects of a slower clock thus not measuring the “real” velocity. Why is that? The result of this choice is that we have “relativity of simultaneity” saying that someone will think that 2 events happened at the same time while another thinks they happened at different times rather than having someone think he was going at one speed and another thinks that he was going at a different speed. The Lorentz equations assume there is a "real" velocity thus there cannot be a "real" length. Is there some reason for that Lorentz/Einstein choice? Transverse Spin Counter If we mount a transverse spin counter on the train and count the number of transverse spins during the train’s 1000 meter run, the Lorentz equations will yield the same number of spins as anyone at the station would count for that same length of time, especially if it is optic, because transverse time isn’t effected by linear motion and certainly optic time isn't. The spin counter would correct for the time dilated slower clock and measure the correct velocity. So can we say that if a train has a spin counter on it, its length, “dx’ “ doesn’t dilate and thus when it believes things are simultaneous they really will be? Our other choice is to say that due to Lorentz equations we must accept “relativity of count” wherein our otherwise unaffected count of anything will have to change merely because we were moving (maybe now we know where that missing passenger went?).