Re: [Phys-l] Relativity Question

[chuck britton <cvbritton@embarqmail.com>]

I'm a bit of a klutz when it comes to the analytical sides of these  
discussions but let me see if a concrete example might give Eric  
something that we can all chew on together.

Einstein used fast trains 'cuz folks back then didn't have rocket  
ships and such for their gedanken experiments.

If a train car has a flashbulb hanging exactly halfway between the  
front and back walls, folks ON the train will measure that a flash  
from that bulb will simultaneously light up the front and back walls.

An observer on the ground will see the back wall illuminated first  
because that wall is moving towards the flash of light.

Eric - does this example help us look at your question in any new light?


		I've always used the Lorentz dilation/contraction approach and  
realized early on that it is the impossibility of simultaneity that  
is often overlooked. There's no nice 'equation' to sum it up as there  
is for time and space intervals.

Two events that are simultaneous in one frame CANNOT be simultaneous  
in ANY OTHER frame.
		(unless of course they are at the same location as well as the same  
time -
		in which case I'll claim that they are only ONE event - not two.)


On May 13, 2009, at May 13(Wed) 5:06 , John Denker wrote:

> On 05/13/2009 12:00 PM, Eric Lane, Lane wrote:
>
> > Can you suggest any tests for validity?
> >
> > We seem to be OK on GPS SR correction. Our theory would seem to
> > accomodate relativity of simultaneity, the latter being defined then
> > as equal values, according to the light equation, of transit times of
> > signals to an observer from two events, simulataneous in the frame of
> > issue.
>
> Well, that right there is a test for validity ... but the test
> is already failed.  If two distinct events are simultaneous
> "in the frame of issue" or any other frame, then there cannot
> be any signals that "transit" from one event to the other.
>
> To say the same thing in modern (post-1908) terminology:  there
> is a spacelike separation between the two events.  The worldline
> of a signal is either timelike or lightlike.