Re: [Phys-l] light clock relativity experiment

["Bob Sciamanda" <trebor@winbeam.com>]

Fink Trevor M asks, regarding a photon clock as viewed from a second Lorentz 
frame:

> My questions is, "If light behaves in such a manner that the velocity of 
> the object emitting it has no effect on its velocity, why does the light 
> not remain at >position x and simply change its y,t values?"  Reworded, 
> "Why does the light travel with the train as opposed to the train moving 
> relative to the light?"

Events are the absolute entities in SR.  All observers will catalogue the 
same events, but different Lorentz observers will assign different 
space-time coordintates to a given event. The two events of interest here 
are
1) the emission of light from a source fixed on the train at  location A, 
and
2) the reception of this light at a second location fixed on the train at 
location B (perhaps triggering a photocell and ringing a bell!)

The second "platform" observer sees these same two events, and can correctly 
describe them by the above descriptions.  But he sees the train (and the 
train locations A and B) travelling along the direction of the train's 
velocity.  Event B must therefore occur further down the railroad track than 
event A.

To assert that the two observers see the light arrive at two different train 
locations would be to assert that they observe two different reception 
events.

Hope this is helpful

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
trebor@winbeam.com
http://www.winbeam.com/~trebor/