Re: constancy of light

YBM a écrit :
rbwinn a écrit :
On May 5, 11:18�am, YBM <ybm...@xxxxxxxx> wrote:
rbwinn wrote:
Einstein's own equations for
velocity of light do not work in the Lorentz equations if x or x' are
negative.
Wrong. They work.

No, they do not work. Einstein said that x=ct, x'=ct'. If x is
negative, then

t'=(t-vx/c^2)/sqrt (1-v^2/c^2)

cannot be used with the equation x=ct. The velocity of light has to
be -c in the equation for t' in order for the equation to work if x is
negative. x=(-c)t, not x=ct.

Wrong.

Let's assume that x=ct

By LT we get :

x'= gamma*(x-vt)
t'= gamma*(t-vx/c^2) where gamma=1/sqrt(1-v^2/c^2)

let's have a look at x'/t' (*) under the condition that x=ct :

x'/t' = (x-vt)/(t-vx^2/c^2) = (ct-vt)/(t-vct/c^2)
obvious typo : ..../(t-vx/c^2) = (ct-vt)/(t-vct/c^2)

= t(c-v)/( t (1 - v/c) ) = c(c-v)/(c-v)
= c

=> x'=ct'


(*) the case t'=0 is trivially ok (0=c0).
.

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