
Can Many-Worlds Theory Rescue Us From Boltzmann Brains? - dnetesn
http://nautil.us/blog/can-many_worlds-theory-rescue-us-from-boltzmann-brains
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snowwrestler
Can one unprovable and arguably imaginary idea save us from another
unproveable and arguably imaginary idea?

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Moshe_Silnorin
Macroscopic decoherence (and therefore many worlds) is a straightforward
prediction of the Schrödinger equation. It's not something you can just
dismiss as imaginary.

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TheOtherHobbes
Apart from that minor "Let's create an infinite number of universes out of
nothing" problem.

Mathematical solutions are never guaranteed to be physical, or even
potentially realisable.

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bmh100
What is your preferred interpretation? Mine is pilot wave, treating the wave
function as a purely mathematical and nonphysical concept.

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Filligree
Pilot wave theory still requires the wavefunction to _exist_ , with all the
same detail as many-worlds, all the same computations. It just then picks a
particular timeline and declares that this one is real, these are real
particles, and everything else is shadows on the wall. It's thus incompatible
with computationalism.

I consider this scenario improbable.

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bmh100
My limited understanding is that the pilot wave is more of a concept regarding
embodied in the exact state of the universe. In other words, the pilot wave is
the seed in the pseudorandom number generator of the universe.

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Filligree
I'll admit it does get a little philosophical, but:

No. The "pilot wave", in pilot wave theory, is a mathematical object
_identical_ to the universal wavefunction of the many-worlds interpretation.
As such, if you believe that computation is all is required for consciousness
to exist (and there's no separate "is real" tag on the math), then it's an
incoherent concept.

I fall on that side myself, but I can't convincingly argue that it's the right
philosophical stance to take. I've yet to see anyone give a _proof_ , it just
seems most likely.

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empath75
I think the logical incoherence of the Boltzmann Brain saves us from it.

1) What we know about the world leads me to the belief that it's far more
likely that a collection of particles in a thermal equilibrium have randomly
and temporarily formed into a brain for an instant, than that the entire
universe exists as I believe it to.

2) Since I am extremely likely to be a boltzmann brain, everything I know
about the world is illusory, and nothing outside of my own mind exists, and my
memories don't represent reality.

3) Therefore, everything I thought I knew about the world which led me to
believe that I am a boltzmann brain is unlikely to be true.

4) I am unlikely to be a boltzmann brain.

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Strilanc
Step (3) is not valid. You can't use "I would reason badly in case A" as a
proof that A can't happen. At best it's an argument that, when deciding what
to do, case A isn't worth worrying about. But that's different from asserting
case A can't have happened.

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bmh100
Intuitively, I feel that it is extremely more probable for a Big Bang, giving
rise to life that knows science, to randomly occur than for a Boltzmann Brain,
self-consistently simulating the evolution of such a universe for billions of
years, to randomly occur. However, it is hard for me to explain that feeling
more precisely.

Maybe it's like this: it is much more likely to randomly simulate a game of
chess where a pawn gets promoted to a queen than it is to randomly generate a
move history from random characters, which resulted in a valid chess game of a
pawn getting promoted to a queen.

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stavrianos
We don't need it to simulate the universe for a billions of years. We just
need it to simulate _your belief that it happened_ for a couple of seconds.

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bmh100
Yes, a belief which relies on logical validity and self-consistency of memory
and thought, which would in turn need to be the result of a "simulation". And
by "need", I really mean "much more likely than the alternative" of producing
such a state otherwise.

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dri_ft
But are you really scanning all of your beliefs for consistency at every
moment? Couldn't you just be presented with a simulated _feeling_ that your
beliefs are consistent? Wouldn't that be enough? It's certainly plausible that
a Boltzmann brain could have that.

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richardlong
Given the internal and logical consistency apparent in this life, it stands to
reason the Boltzmann brain would have to be simulating the entire thing -- the
thought processes of other people, countries, wildlife, the movement of the
stars, and so on.

Absent some calculation cost, which Boltzmann brains don't seem to provide,
there's no reason everything wouldn't be fully rendered inside the Boltzmann
brain.

At some point you just have a God, and are right back at old-timey religion,
not that there's anything wrong with that.

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macawfish
Is a Boltzmann brain by definition unstable? Over what timescales? While it
exists, does it function within its presumably more stable context, or is it
somehow magically disengaged from its context in a way that necessitates
instability?

What I'm getting at is that the idea of a Boltzmann brain, as juxtaposed with
a "real brain", seems a little too " classical binary logic" for a universe
that evolves. Perhaps some of our most resilient features have evolved with
the help of spontaneous Boltzmann-brain-like intuitions, whims, or setups, but
have been since then integrated in a stable way.

I imagine a Boltzmann brain to be something like a spark, but not immune from
outside interaction or influence. Am I missing something?

What happens if a Boltzmann brain "catches on"? Is it still a Boltzmann brain,
now that it has contextualized itself in a stable way? Was it ever a Boltzmann
brain?

This also comes down to the meaning of "randomness", and I don't think the
mathematical jury is quite out on that subject.

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Symmetry
I'll point out that Botlzmann brains are only something you would ever think
about in a universe going through a graceful heat death rather than the
equally likely big crunch or big rip scenarios.

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bmh100
Dark energy suggests that a big crunch is unlikely.

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Filligree
A big rip, on the other hand...

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bmh100
Last I read, there is too much uncertainty in measurement to tell them apart.
It will have to be resolved theoretically, since a heat death will only be the
final result when omega exactly equals -1.

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jwilk
[https://en.wikipedia.org/wiki/Betteridge's_law_of_headlines](https://en.wikipedia.org/wiki/Betteridge's_law_of_headlines)

