Originally posted by John Martin
I assume by c you mean speed of light, and (x,y,z,t) and (x',y',z',t') is the same point after a lorentz transformation, with v being the velocity of something at that point.
In that case, yes, c would be the same after a lorentz transformation, because its invariant. However v would only be the case if v is c, or if the lorentz transformation takes one to the same reference frame. In other words, it does nothing.
If v is not c, then v' would be different quantity than v, as it would be changed by the lorentz transformation.
As St. Thomas Aquinas would say, a mistake in the beginning is a mistake indeed.
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