On May 5, 9:08�pm, The Ghost In The Machine
wrote:
In sci.physics.relativity, rbwinn

�wrote
on Mon, 5 May 2008 13:30:45 -0700 (PDT)
:





On May 5, 12:07�pm, YBM wrote:
rbwinn a �crit :

On May 5, 11:18?am, YBM 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)
� � � � = t(c-v)/( t (1 - v/c) ) = c(c-v)/(c-v)
� � � � = c

= x'=ct'

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

You neglect the fact that if x or x' is negative in the equations
x=ct, x'=ct', then either the velocity of light has to be negative or
time has to be negative.

The substitution x^2 = c^2t^2 works equally well, yielding
x'^2 = c^2t'^2. �This is a more accurate specification of the
problem anyway, as light expands spherically from a point source.

[rest snipped]

Well, what about a photon traveling in the +x direction reflected by a
mirror back in the direction it came from? I would just say it had a
velocity of -c.
I know that c^2 seems like a good idea to scientists. (-c)^2=c^2
Robert B. Winn