Re: A Geometrical Proof of the Non-invariance of the Spacetime Interval

[Bob LaMontagne <rlamont@POSTOFFICE.PROVIDENCE.EDU>]

David Rutherford wrote:

> > Let me make the example more
> > specific. The F' people in the trailer drop a stone. When it hits the floor it shakes
> > dirt loose from the bottom of the trailer and it falls on the ground (F frame). Later,
> > F' drops another stone on top of the first and again dirt is loosened and falls to the
> > ground. F' measures a distance of 0 between the stones (they lie on top of each
> > other).
>
> F also measures a distance of 0 (in the x-direction) between the stones,
> since they're on top of each other in F, as well.
>
> > F measures about a mile between the patches of dirt.
>
> F' can't see the patches of dirt, anymore, since his hole has passed
> them by. So he has no idea how far apart they are. If he could see them,
> he would say that they are (nearly) a mile apart.

F and F' are looking at events. Since they can't communicate through the solid walls of the trailer, they can
only measure the (Galilean) distance between the events by the indicators in their own frames of reference - the
stones for F' and the dirt patches for F.

If F' somehow sees the patches of dirt, he is simply getting information as to how F separates the events. That
is valid information, but it doesn't alter his own measure of the separation of events from his frame - which is
0.

Reading back through the previous posts, this seems to be the source of your anomalous result for the spacetime
interval.  You're having a person in one frame measure the separation as seen by the other person and then using
that measure as their own - which it isn't.

Bob at PC