Re: Variable speed of light (was: Relativity conundrum)

[Michael Burns-Kaurin <mburns-k@SPELMAN.EDU>]

I would add to Bob's reply that, since the events of entering the train and
leaving the train do not occur at the same place in the train frame, then
the time dilation factor is not enough--one must also consider the position
term in the Lorentz transformation for time.  When dealing with situations
such as this, one should use the transformations and not rely on length
contraction and time dilation.

Michael Burns-Kaurin
Spelman College





Pentcho Valev wrote:

> There is a version which could be a thought experiment and which
unequivocally
> shows that the speed of light is not constant. In the rest (railway)
frame the
> beam approaches the train at a right angle so that, in the train frame,
it moves
> obliquely. Consider two events - the beam entering the train and the beam
> leaving the train - registered in both frames. Obviously x < x', where x
is the
> distance the beam travels between the two events in the rest frame and x'
is the
> respective distance in the moving frame. The time measured in the rest
frame for
> the travel x is t, and that measured in the moving frame for the travel
x' is
> t'. If there is time dilation, t' < t and, accordingly,
>
> c = x/t < x'/t' = c'

Just for the sake of the argument, assume that the numerical value of the
speed of
light is the same in the two frames. then, in the frame where the light
moves
obliquely, the light must travel a longer distance, x', and hence must take
a
proportionately longer time, t', to travel that longer distance. The ratio
x'/t'
would therefore remain the same as x/t (because x' > x and t' > t). Time
dilation
really is not a consideration here, and t' is definitely not less than t.
Even if
time dilation was applied (which would also require considering a length
contraction
of the component of obliqueness parallel to the train's motion), t' > t
still holds.

Your assumption of t' < t is what's leading to the differing values for c
and c'.

 Bob at PC