Re: "a mist of probability amplitudes"

From: Mitchell Porter (
Date: Tue Apr 06 2004 - 08:47:24 MDT

Tyrone Pow:

>I guess metaphors and not-so-subtle abstractions are lost on some people.

Eliezer is stating the views of physicist Julian Barbour. He believes in a

  dualistic picture of Platonia, the collection of all possible
  of the universe, and the completely different wave function, conceived
  of as 'mist' over Platonia... In answer to the question 'what is real?', I
  answer 'configurations'. (Barbour, "The End of Time", p.228 or so)

So Barbour believes in a many-worlds theory in which time is an illusion.
This is what exists: all possible spatial (not space-time) geometries, and
a complex number attached to each one (the 'probability amplitude').

In ordinary quantum mechanics, you take the absolute value of that
complex number and square it, to get a probability. But in a many-worlds
theory, all the possibilities are equally real. So those numbers attached
to all the worlds can't be probabilities. But then what are they? Well,
maybe they're a "measure", such as is used in integration - a way to
"count" a continuous infinity of objects. If so, I'd like to see an argument
that the proposed wavefunction of the universe makes sense as a measure,
but okay, I could accept that. But then don't call those mystery numbers

And then there's the part about time being an illusion. I don't know
what to call that... Implausible? Outlandish? Absurd? It is hard to think
of a phenomenon more basic than "Things change", except perhaps
for "Something exists". So I object very strongly when a bizarre metaphysics
like Barbour's is passed off as what physics says and as something that is
proven. And let's be a little clearer than "Life is a mist of probability
amplitudes". How about: "Life is an infinite number of disconnected and
unchanging universes, each with an extraneous number attached; and
each moment of your life is located in a different one, and not actually
connected to any other such moment."

Recommended reading:

What's your house worth? Click here to find out:

This archive was generated by hypermail 2.1.5 : Wed Jul 17 2013 - 04:00:46 MDT