**From:** Mitchell Porter (*mitchtemporarily@hotmail.com*)

**Date:** Tue Apr 06 2004 - 08:47:24 MDT

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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

configurations

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

"probabilities"!

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:

http://www.maths.unsw.edu.au/~jim/wrongthoughts.html

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