"The problem is to explain also why the entropy of the early universe was
so low. If you just accept that this is the case and also don't bother
about the very distant future, there is no problem. But if you assume that
time goes on from the infinite distant past and/or to the infinite distant
future, you have a problem, because smaller local low entropy states are
then more likely than the whole observable universe being in some low
That make me think about the people that try to discover the whys of the
arrow of time by taking concepts like "beginning of the universe". That
presuposses the arrow of time that he is trying to demonstrate how it
arises in the first place. this is a circular reasoning. All that he can
demonstrate empirically is that it follows entropy, an then, he is puzzled
by the fact that entropy was so low at the "beginning"
but if we take the idea of a block universe shaped as a four dimensional
bell with a singularity in the left ( see the figure that I linked), there
is no arrow of time here. is our life that goes along very short segments
from left to right in the middle of this figure. what we do is to
extrapolate this sort segment to the whole figure. But this is not right.
first, time is local, according with general relativity. How we extrapolate
it? by assuming that time progress in the universe in the direction that
we perceive causality, that is, in the direction of entropy increase.
but even so, there is not a single arrow of time where entropy increases.
there are infinite lines of entropy increase/arrows of time departin from
the singularity, which diverge radially trough the bell and extend to the
right in the figure.
If i´m right, the existence of a gradient of entropy and, thus the
existence of a singularity with maximum entropy somewhere, at a point which
we consider "origin of the universe", is a pre-requisite for natural
selection and life. Natural selection (as I said before) select "good
correlations" which deal with macroscopical events, to design life and
observers. That is why we see this universe with such unavoidable notion of
beginning and not other in other ways.
A boltzman brain is just a curiosity, unless the bolzman fluctionation
create not a single brain but a local portion of the universe that develop
in a way that maintain intellgent beings. In this case, it
is indistinguishable if the universe is or not the product of a boltzman
2012/7/31 Bruno Marchal <marc...@ulb.ac.be>
> On 31 Jul 2012, at 17:36, smi...@zonnet.nl wrote:
> Citeren Bruno Marchal <marc...@ulb.ac.be>:
>>> On 30 Jul 2012, at 19:57, meekerdb wrote:
>>> On 7/30/2012 2:19 AM, Alberto G. Corona wrote:
>>>>> The Boltzman brains , according with what i have read, are completely
>>>>> different beasts. Boltzman pressuposes, that , since no random
>>>>> of matter is statistically impossible, and Boltzman demonstrated it in
>>>>> certain conditions (ergodic conditions) , with enough time, some
>>>>> arrangements of matter would simulate minds, or even worlds and
>>>>> civilizations. But 15.000 Million years, that is the age of the universe
>>>>> is not enough.
>>>> Boltzman was considering the question of how the universe came to be
>>>> in its state of low entropy. I could be due to a random fluctuation.
>>>> And it was more probable that the random fluctuation simply produced the
>>>> universe as we see than a fluctuation that produced a big bang universe
>>>> which then evolved into what we see.
>>> Actually I doubt this, like the probability that life appears on earth
>>> and leads to us, is plausibly bigger than the probability that "I"
>>> appears here just now, in my exact current state.
>>> And extending this line of thought further, a fluctuation that merely
>>>> created a brain along with the illusion of this universe was still more
>>>> probable (i.e. less improbable).
>>> If that were true, that could be used to put more doubt on the
>>> existence of the 1-person indeterminacy measure, I think.
>>> In the UD, or arithmetic, this reflects the competition between little
>>> numbers (simple explanation) and big numbers (algorithmically complex
>>> explanation). But the indeterminacy bears on all numbers, so the little
>>> one have to multiply much more than the complex one, in some ways.
>>> Linearity at the physical bottom might be explained by that phenomenon,
>>>> Sean Carroll has a good discussion of this and why this argument does
>>>> not hold for a multiverse, in his book "From Infinity to Here".
>>> Looks interesting. I guess this can be very easily extended to the
>>> "many dreams" occurring in arithmetic.
>>> http://iridia.ulb.ac.be/~**marchal/ <http://iridia.ulb.ac.be/~marchal/>
>> The problem is to explain also why the entropy of the early universe was
>> so low. If you just accept that this is the case and also don't bother
>> about the very distant future, there is no problem. But if you assume that
>> time goes on from the infinite distant past and/or to the infinite distant
>> future, you have a problem, because smaller local low entropy states are
>> then more likely than the whole observable universe being in some low
>> entropy state.
>> And Sean Carroll's argument amounts to simply hiding the problem in an
>> ever expanding state space, it's not that he has shown that in a multiverse
>> the problem doesn't occur.
> But with comp I don't see how we could avoid the ever expanding state
> space. That is what a UD is, notably, and its existence is a consequence of
> simple laws (+ and *).
> Should not a quantum multiverse also contains some quantum universal
> dovetailer and avoids the problem in the Sean Carroll way? (as far as I can
> imagine it)
> http://iridia.ulb.ac.be/~**marchal/ <http://iridia.ulb.ac.be/~marchal/>
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