Re: relativity of simultaneity

gsax wrote:
> Hi
>
> I am newbie to relativity..
> I have a question regarding simultaniety..
>
> If the Happeninng of an Event C( say lighting of a bulb), depended
> upon whether or not two events A & B occur simultaneously,...then does
> C happen or not ( since simultaneity is relative)..
>

> Let's say in frame 1, A & B occur simultaneously, then C happens ( The
> bulb lights up)..
>
> Also let's say in frame 2, A & B do not happen simultaneously, then C
> does not happen ( THe bulb does not light up)..
>
> But either the bulb lights up, or it does not,.. which is it?
>
> thanks
> Gaurav

Nice question relating to a fundamental idea of SR.

The key is that the bulb lights up if two events are simultaneous IN
FRAME 1 (its rest frame). The fact that the two events are not
simultaneous in frame 2 is irrelevent.

The lighting of the bulb is a physical event that can have consequences
e.g. exposing a piece of film. The two observers can get together at
some later time after the experiment to examine the bulb and they would
agree if it were lit or not.

The point is that the observer in frame 2 knows his relative velocity
w.r.t. frame 1 and can therefore, using SR, determine that the two
events are simultaneous in frame 1. He would therefore agree that the
bulb should light up.

P.S. Just finished with Mermin's book (Space and Time in Special
Relativity). He gives a lot of examples showing how each of two
inertial observers would calculate what the other one measured.

.

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