On 25 Mar 2014, at 06:58, chris peck wrote:
>>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.
I agree. here comp is infinitely more risky, as it predicts exactly
what is physics. Only if this gives classical propositional logic, the
MW would become a trivial idea explaining nothing in the local
geography. But that risk has been taken, and we know now, that there
is a non trivial physical (notably) reality. We know more: that its
bottom core is quantized and symmetrical. It is matter of time to see
if some quantum computer inhabits there or not.
Bruno
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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