[extropy-chat] Boltzmann Brains

Russell Wallace russell.wallace at gmail.com
Thu Feb 22 03:15:12 UTC 2007


Interesting! Though it still seems intuitively reasonable that it should be
easier to create something simple by vacuum fluctuation (like a
submicroscopic pocket of false vacuum) than something complex (like a
conscious brain); given that a pocket of the right sort of false vacuum can
lead to a Big Bang which can lead in turn to many ordinary observers, that
would seem to explain why ordinary observers can still outnumber Boltzmann
brains.

On the other hand, I've seen it said a few times that the probability of a
pocket of false vacuum has a double-exponential, exp(exp(X)) where X is
about 10^50 or so (the temperature differential between super-hot Big Bang
false vacuum and super-cold intergalactic space); I would have expected it
to be merely exp(X). One kind soul did try to explain the reason to me, but
I lacked the background to understand the explanation. I don't know whether
that's a relevant area to focus on.

The theory presented in the linked article doesn't sound right to me, and
here's why: They predict the half-life of the universe to vacuum decay is
not much greater than the current age of the universe.

But the _expected_ half-life is presumably not much less than the current
age, or we would have evolved earlier than we did. Since it seems improbable
that the expected half-life just happens to be on the same order as the
timescale for evolution, I predict the actual half-life is (as suggested by
current semi-mainstream theory) much greater than the current age of the
universe.
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