Cosmology and Boltzmann brains

From: Günther Greindl <guenther.greindl.domain.name.hidden>
Date: Thu, 12 Jun 2008 23:43:26 +0200

Hi all,

someone on another list alerted me to this post, there is a very
interesting discussion going on on that blog related to Observer Moments:

http://golem.ph.utexas.edu/category/2008/06/urban_myths_in_contemporary_co.html

Greg Egan has posted too; and has some very interesting things to say.
Specifically, he says the right things why DA fails:

http://golem.ph.utexas.edu/category/2008/06/urban_myths_in_contemporary_co.html#c017260

"The fact that an observer selected at random from the pool of all
observers would be more likely to be class 2 under theory A is
irrelevant; nobody has to “select us at random” before we’re allowed to
make an observation."

And here:
http://golem.ph.utexas.edu/category/2008/06/urban_myths_in_contemporary_co.html#c017310

"There is one aspect of the BB argument that is independent of these
issues, though; rather than debating whether far-future life will be
“freakish” or “Darwinian”, if we accept an infinite or extremely long
future in which observers of any kind are present – so long as they can
make observations that show them that they are not living in the early
universe – then “typicality” is not a matter of being a Boltzmann brain
or a Darwinian brain, but simply whether you are living in the early
universe or the later universe.


The way the BB fans use probability, they would then argue that the
universe is very unlikely to have this very long extended future,
because then a “typical” observer would live in the far future … making
us “atypical” because we live in the early universe. I guess that’s
really just a variant of the infamous Doomsday argument, applied to the
universe as a whole: the universe is unlikely to last very long,
otherwise it would be “unlikely” for us to find ourselves so near the
beginning. That’s where I think they’re simply misusing probability:
we are not a random selection of observers taken from the entire history
of the universe."


That is what I think is the real problem with DA arguments: it is a
decision strategy; but OM's are not playing games ;-); they do
reasoning; and while this strategy would assure that most OM's are
correct, it is not very satisfactory for the current OM - it only gains
knowledge about optimal strategy, but not of it's _concrete_ situation.

That is why I think RSSA is better than ASSA. But RSSA is still not
satisfactory. Hmm; this whole continuation of experience business is the
whole mystery anyway IMHO.

Cheers,
Günther




-- 
Günther Greindl
Department of Philosophy of Science
University of Vienna
guenther.greindl.domain.name.hidden
http://www.univie.ac.at/Wissenschaftstheorie/
Blog: http://dao.complexitystudies.org/
Site: http://www.complexitystudies.org
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Received on Thu Jun 12 2008 - 17:45:05 PDT

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