Re: TECH: Quantum Head Job

From: Andrew Clough (
Date: Sun Oct 14 2001 - 16:01:29 MDT

At 12:42 PM 10/14/2001 -0400, you wrote:
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>John Clark wrote:
> >
> > Adrian Tymes <>
> >
> > > And here is where our information diverges. If, indeed,
> modifying the
> > > spin is impossible for Alice, then you are right: that method won't
> > > work. If it is possible to modify the spin, then your argument falls
> > > apart on that statement.
> >
> > If it was possible to change the spin at will of an entangled particle
> without
> > destroying the delicate entanglement with its twin then yes, I could indeed
> > communicate faster than light. If that were possible I could do even
> communicate
> > with the past. If that were possible I could send you a reply to your
> post before
> > you had even written it .
>How could you communicate with the past. Causality is not violated even
>when light speed limits are in entanglement.

I'm not sure what you mean by that last part of that last sentence: "Light
speed limits are in entanglement." I didn't think physical constants like
c, permitivity, and permeability could be entangled.

Anyway, I can see a way to communicate with the past using instantaneous
communication. First, send the message to your past self to a friendly
probe/alien/space craft Very Far Away. Next, have this second party change
their velocity be a Good Deal. This will change what is considered
"simultaneous" with them. (Actually, I believe non-local simultaneity is no
longer a valid concept because of this, much like absolute frames of
reference.) They can then be simultaneous with you past self, and can
relay the message to him or her.

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