Re: A Geometrical Proof of the Non-invariance of the Spacetime In terval

["RAUBER, JOEL" <JOEL_RAUBER@SDSTATE.EDU>]

David wrote in response to Hugh:


> I'm not denying that you _can_ say that you had breakfast and lunch in
> the same place. I'm arguing that it's not valid,
> geometrically to do so.
> When you (the moving observer) determine the spatial distance between
> breakfast and lunch at lunchtime, you put the breakfast end
> of the tape
> measure at San Diego, not Los Angeles, and the lunch end of the tape
> measure at San Diego. The Los Angeles observers put the
> breakfast end of
> the tape measure at Los Angeles and the lunch end of the tape
> measure at
> San Diego. The locations, in space, of breakfast at the time of lunch,
> are what both frames consider to have been the locations of breakfast,
> at the time of breakfast, since both frames say that the
> locations have
> not changed, in their frame, since the time of breakfast.

Which strikes me (except for the last sentence below) as a quasi-proof of
John M's statement

<JM> "Clearly then, the spatial distance between two events is a
frame-dependent quantity."


> These
> locations don't coincide in space, thus, they don't coincide in
> spacetime.

Above you just "proved" that the two events coincide in space for F' but not
for F. So this last statement contradicts your above reasoning.

Joel R.