Re: A Question of Simultaneity

[John Mallinckrodt <ajmallinckro@CSUPOMONA.EDU>]

> 1. If the flashes end up simultaneously at O in the train reference frame,
> do they end up simultaneously at O in all reference frames?

Yes.  We can name the event "The two light flashes arrive at O"
without ambiguity.  It specifies *a* time and *a* place.  Other
observers may use different coordinates to specify *that* time and
*that* place, but they must necessarily agree that there is a
single event that is unambiguously named "The two light flashes
arrive at O".

> 2. If the speed of the flash pulse along the train is c in the train
> reference frame, is the speed also c in a reference frame moving at speed v
> relative to the train?

Yes.  The speed of light is the same in all reference frames.

> 3. If the distance from O to the left-most point is the same as the distance
> from O to the right-most point, is the ratio of the distances also 1 in a
> reference frame moving at speed v relative to the train?

Yes.  Both contract by the same factor so the ratio remains one.

> Can all three be true?

Evidently!

John Mallinckrodt      mailto:ajm@csupomona.edu
Cal Poly Pomona          http://www.csupomona.edu/~ajm