Re: Variable speed of light

[Pentcho Valev <pvalev@BAS.BG>]

"John S. Denker" wrote:

> Originally 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.
>
> OK down to here
>
>  >> 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'
>
>
>
> The answer is that t' is greater than t.  For observers
> aboard the train, there is nothing to explain;  they
> just measure t' in the obvious way, relative to their
> own lattice of rods and clocks.

Just a small remark (later I hope to be able to write more). In textbooks, one
finds essentially the following statement: "While  clocks in the rest frame
tick 5 times, clocks on the (very fast) train tick only once". Doesn't this
mean that t' < t? If it doesn't, textbooks appear to be fatally confused.

Pentcho