[ExI] QT and SR

Lee Corbin lcorbin at rawbw.com
Tue Sep 9 21:57:11 UTC 2008

Stathis writes

> 2008/9/8 scerir <scerir at libero.it>:
>> Stathis:
>>> But in the MWI, in one world you definitely chose A
>>> and in the other you definitely chose B. It still feels
>>> as if you had a "free" choice because you only experience
>>> one world at a time, but that's just an illusion.
>>> The distal electron will always correlate with your
>>> electron, because all along it was in either the universe
>>> where you made the A measurement or in the universe where
>>> you made the B measurement.

(Which wording I don't quite agree with, though I suspect that
Stathis and I are in the same univ..., er, on the same page.)

>> In EPR experiments there are two measurements (Alice
>> performs her measurement here, Bob performs his
>> measurement in a spacelike separated region). Can MWI
>> say which, between Alice and Bob, performed his
>> measurement first and which then? I do not think so.
>> So, in the sentence "in a world *you* definitely chose A
>> and in the other *you* definitely chose B" those *you*
>> refer to both Alice and Bob, isn't it?
> There are many Alices and Bobs all doing their own thing every which
> way, but when they actually meet up, we find that their results always
> correlate. It's the fact of this correlation when they meet up that
> shows they are in the same world.

They're in the same world *now*.

> It's tempting to add, as I did above, that therefore they must have
> been in the same world all along,

My only objection to your phrase is that until a measurement is
conducted here, r'chere there is but one "branch", and we usually
say that it bifurcates here when the measurement is performed,
yielding an Alice-a and an Alice-b right here. Likewise, there,
until a measurement is performed there, only a single branch exists
there. But when (or if, I guess) they go ahead yonder, then a Bob-a
and a Bob-b will develop from Bob too over there.

> but I can see on reflection that this is not meaningful while they are
> spacelike separated.

While they are still spacelike separated is when we assume 
that the measurement(s) take place; that is, in other words,
the splitting occurs *first* neither here nor there, but outside
each other's light cones. So like I was saying before, the
Alices and Bobs---outside the light cones of each other's
respective measurement events--- remain single and then
become dual, all before getting any light signals from each other.


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