This post is an reaction to another blog article of Lubos Motl, where he presents a Richard Feynman's lecture about arrow of time. At the beginning of the third part, Feynman explains, why Boltzmann brain is a "ridiculous theory", because it "incorrectly predicts", that the rest of the world should be completely disordered. We can see this as a another demonstration of Popper's methodology symmetry, where every negation of theory becomes new testable theory as well. So that not only validity of theory - but the validity of all arguments against theory must be allways checked carefully. If we consider every logical theory wrong from its very beginning, the objective stance becomes biased quite often.
As I explained previously here and specially to Lubos, Boltzmann brain hypothesis has nothing to do with situation, when 10^{23} particles will get organized suddenly into something like human brain. It describes the situation, when unspecified amount of particles is involved into Boltzmann brain creation. When we consider 10^{23*23} particles, the probability of formation of some particular configuration of just 10^{23} particles will be unitary - so we can say safely, the existence of human brain in every 10^{23*23} particles of matter will become undeniable. This number roughly corresponds the number of particles inside of observable part of Universe and the number of string theory possible solutions, which could serve for falsification of this concept. So we can interpret both Universe, both human brains entities as a product of random fluctuations of hypothetical particle gas - which is basically what the whole AWT is about.
Among other things, this approach explains, why every large group of people tends to check all meaningful answers and theories, before the most relevant one is considered at the very end. This is because the intelligent stance of individuals in every large group of people is compensating mutually, so that such group is behaving like chaotic Boltzmann gas as a whole. This can explain, why Aether theory was recognized so early in human society - but understood and accepted so late.
Every brain can see (i.e. to interact via transversal waves with) just the causal portion of Universe, which corresponds the causality of Boltzmann brain hypothesis - so we can expect, if we find an even more general approach later, it could predict even larger number of states, then the random walk model considers - our causual Universe would expand with time. Because of nested character of density fluctuations of Boltzmann gas - which undergoes a Maxwell-Boltzmann distribution - our Boltzmann brains could never see the rest of our environment empty, "completely random" the less - particularly because both Feynman, both Motl didn't realize, their intepretation considers no environment at all. I do believe, virtually every human brain (including this one of average string theorist) could understand the difference between Boltzmann and Feynman approach to random Universe and stop to misinterpret this simple, yet powerful theory.
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