>>I think you're missing Scott's point. The universe is obviously
isomorphic to a mathematical structure, in fact infinitely many
different mathematical structures, all of which are in Borges
Library of Babel. Almost all of them are just lists of what
happens. Scott's point is that this is not very interesting,
important, or impressive. It's only some small elegant compression
of those lists that's interesting - if it exists. Scott seems to
think that it does. I think it does *only* because we're willing to
call a lot of stuff "geography" as Bruno puts it, aka boundary
conditions, symmetry breaking, randomness...
Hmm, I just read Scott as saying that MUH is scientifically empty in the sense
that it makes no significant predictions, the emphasis being on the word
significant. The predictions it does make are a little wishy washy. Like, MUH
predicts that science will continue to uncover mathematically describable
regularities in nature. what would a non-mathematically describable law look
like? And how is a mathematically describable regularity in this universe
evidence of the existence of another mathematical universe? He also takes
Tegmark to task on his use of anthropic reasoning because it allows Tegmark to
have his cake and to eat it. The extent to which regularities are elegantly
described by maths will be taken as evidence for an inherently mathematical
ontology. The extent to which they are not will allow him to invoke the
anthropic principle and say well it would be absurdly lucky that the one
universe that existed just happened to have these wierd constants that
supported life.
I think in Popperian terminology Tegmark's predictions just are not risky
enough. He's guaranteed to hit one or the other every time.
I'll be interested in how Tegmark addresses Scott's last point concerning the
physicality of universes beyond the cosmic horizon.
I can see both points of view. I can appreciate Tegmark's view that a galaxy 1
light year beyond the cosmic horizon is just like Andromeda but just a bit
further away.
On the other hand I also see Scott's point that if it is just far enough away
to prevent any causal interaction then it doesn't satisfy a reasonable
definition of physical. To be physical is to be causally relevant. There
doesn't seem to be much semantic difference between a non physical universe and
one which is so far away that it couldn't ever effect us.
Date: Tue, 25 Mar 2014 16:57:05 +1300
Subject: Re: Scott Aaronson vs. Max Tegmark
From: [email protected]
To: [email protected]
On 25 March 2014 16:40, meekerdb <[email protected]> wrote:
On 3/24/2014 8:24 PM, LizR wrote:
"But Tegmark goes further. He doesn't say that the
universe is "isomorphic" to a mathematical structure; he
says that it is that structure, that its physical
and mathematical existence are the same thing."
I can see the appeal. If the universe ever does prove
to be isomorphic to a mathematical structure (and I'm sure
that's a long, long, long way from being proved at present) -
by which I mean, if the universe is exactly described
by said structure, with nothing else needed to completely
describe reality - at that point, at least, I would take Max's
MUH seriously, if only because Ockham's razor would indicate
there was no point in hypothesising the existence of two
things that are exactly isomosphic.
I think you're missing Scott's point. The universe is obviously
isomorphic to a mathematical structure, in fact infinitely many
different mathematical structures, all of which are in Borges
Library of Babel. Almost all of them are just lists of what
happens. Scott's point is that this is not very interesting,
important, or impressive. It's only some small elegant compression
of those lists that's interesting - if it exists. Scott seems to
think that it does. I think it does *only* because we're willing to
call a lot of stuff "geography" as Bruno puts it, aka boundary
conditions, symmetry breaking, randomness...
Yes, if that's his point I am missing it, because although that may be true it
isn't addressing what the MUH claims (at least making the rather large
assumption that I've understood it correctly).
The MUH as I (perhaps mis-) understand it appears to assume there is some
minimal mathematical representation of the universe (known as the laws of
physics or TOE or whatver), and that this exists in a manner that allows us to
differentiate it from geography - as it seems to, at least for the physical
constants that don't appear to vary with time or space, etc. So one has at
least got what may be called local laws of physics and local geography as a
starting point.
If the laws of physics are (somehow - via fire breathing or whatever) able to
generate all possible resulting universes, then we have an explanation for all
the "geography" (modulo our particular position in the string landscape etc),
but presumably (as per Russell's "Theory of Nothing") it all cancels out,
assuming that all possibilities are realised.
However we are a long way from that point, and I imagine the
nature of knowledge and measurement and so on mean that we can
never actually reach it with 100% certainty.
We can't reach it because reaching it via infinite lists of what
happens isn't worth the trip.
Sure, but the MUH assumes there is a unique set of laws of physics, and the
infinite lists all cancel out. (I think one should attempt to criticise a
theory in terms of what it actually says rather than some other
characterisation, surely?)
Brent
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