🚀 go-pugleaf

In article <jtwamley.711766649@adelphi> jtwamley@physics.adelaide.edu.au (Jason Twamley) writes:
>Question:
>Assume the the while universe can be described by a quantum theory....
(Lots of stuff deleted here.  Let me summarize.)

The question, as I understand it, is this:  If we had a theory that predicted the
wavefunction of the Universe uniquely at time t=0, would that mean that the 
evolution of the Universe thereafter was completely deterministic?

Admittedly, we're in somewhat murky waters here, but I'll give an opinion.

No.  The indeterminism of quantum mechanics would still apply.  Let's suppose
that either the standard "collapse" interpretation or the so-called "many-worlds"
interpretation of quantum mechanics is right.  In the first case, observations
will (frequently) cause the collapse of the wavefunction, and this collapse
will be a nondeterministic event.  It is perhaps even more unclear than usual
what counts as an "observation" that can collapse this wavefunction, but the
fact that the wavefunction collapses under some circumstances is certain.

I'm not really up on the many-worlds interpretation, but my understanding of it
is that the evolution of the wavefunction is deterministic, but that the results
of any particular quantum experiment will still be random.  This is true whether
the wavefunction in question belongs to a single electron or the entire Universe.
If anybody wants to do a better job explaining this, be my guest.

-Ted
(ted@physics.berkeley.edu)