From: Mitchell Porter (mitch@thehub.com.au)
Date: Wed Jan 29 1997 - 22:58:29 MST
[John K Clark, to Omega]
> I agree that there is no way, absolutely no way Einstein would say there was
> " a zero spacetime interval" between Earth and the virgo cluster, but what
> about Cramer? If Cramer were to say there was a zero time difference between
> earth and what we see in the Virgo cluster then time does not change, it also
> stops being a useful concept, but I still see the symbol "t" , for time in
> his equations, and he sure doesn't treat it like a constant equal to zero.
>
> If the spatial distance to the Virgo cluster is zero then the concept of
> distance never changes and is always equal to zero, but you see the symbol
> "L" for length in his equations and he sure doesn't treat it like a constant
> equal to zero.
>
> If there was " a zero spacetime interval" between Earth and the virgo cluster,
> then all of spacetime would be a single mathematical point, points have no
> internal structure so the idea of spacetime would not be a useful concept.
Well, the answer to this problem is that distance is path-dependent. If
you take a spacelike path from here to the Virgo cluster, the spacetime
length isn't zero, but if you proceed along Earth's future light-cone
to a point where it intersects the Virgo cluster's future light-cone,
and follow a lightlike trajectory backwards in time into the Virgo cluster
itself, you've travelled on two paths, each of which has spacetime "length"
of zero.
I think bidirectional local causality is an ingenious idea, but what
bothers me about the transactional interpretation when it's compared to,
say, Bohm's theory, is that it doesn't really have an exact mathematical
formulation yet. Cramer suggests that you could decompose a wavefunction
into advanced and retarded components which altogether constitute a
back-and-forth-in-time "causal sequence", but nowhere that I have seen
does he propose a formula or an algorithm for such decomposition.
Something I'd like to figure out: how the operation of quantum computers
would be understood in the transactional interpretation. Would it be
that the readout operation retrocausally determines which computations
are performed...? John Cramer has e-mail, I'll ask him what HE thinks.
-mitch
http://www.thehub.com.au/~mitch/qm.html
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