Boltzmann brains

From: Russell Standish <>
Date: Thu, 31 May 2007 21:51:01 +1000

I came across a reference to Boltzmann brains in a recent issue of New
Scientist. The piece, quoted in full is:

Spikes in space-time

There is another way to think about why our universe began in a highly
ordered or "low entropy" state. In 2002, a group of physicists led by
Leonard Susskind at Stanford University in California proposed that
entities capable of observing the universe could arise via random
thermal fluctuations, as opposed to the big bang, galaxy formation and
evolution. This idea has been explored by others, including Don Page
at the University of Alberta in Edmonton, Canada. Some researchers
argue that under certain conditions, self-aware entities in the form
of disembodied spikes in space-time - "Boltzmann brains" - are more
likely to emerge than complex life forms. Because they depend on
fluctuations of particles, Boltzmann brains would be more common in
regions of high entropy than low entropy. If the universe had started
out in a state of high entropy, it would be more likely to be
populated by Boltzmann brains than life forms like us, which suggests
that the entropy of our early universe had to be low. As a low-entropy
initial state is unlikely, though, this also implies that there are a
huge number of other universes out there that are unsuitable for us.

It seemed to me that a Boltzmann brain was none other than one of our
white rabbits, or at least very closely related. Any thoughts?

A/Prof Russell Standish                  Phone 0425 253119 (mobile)
UNSW SYDNEY 2052         
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Received on Thu May 31 2007 - 18:13:43 PDT

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