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If a Boltzmann Brain existence is fleeting due to the absence of supporting organs and environment, how does the thought experiment account for the passage of time it experience in its brief existence? Even if the brain pops into existence complete with a lifetime worth of memory, how does it explain going through those memory as if one is living through them one day at a time?

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    $\begingroup$ I think it is appropriate to be highly skeptical whether the "Boltzmann brain" idea is able to give any useful insight into any aspect of physical behaviour. This is because it is based on mathematical conjuring with physical ideas well outside the region where we have any confident knowledge of their physical applicability. $\endgroup$ Commented Feb 6, 2023 at 10:48
  • $\begingroup$ I agree. I'm just curious about its consistency as a thought experiment. $\endgroup$
    – bassfocus
    Commented Feb 6, 2023 at 11:07
  • $\begingroup$ Related: the omphalos hypothesis. If you're curious about this idea you might post about it on Philosophy instead. $\endgroup$ Commented Feb 6, 2023 at 13:24
  • $\begingroup$ @Michael Seifert, thanks for the link. I did not know about the Omphalos Hypothesis. Interesting. $\endgroup$
    – bassfocus
    Commented Feb 6, 2023 at 15:15

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Well, if you think about it carefully, you will realize you only ever have the experience of the passage of time in the current moment. You never have any experience of passage of time in a past moment, you only have a memory of said experience, even if the experience seems to have taken place just a split second ago. This memory of the past does not need to be real (formed by an actual experience), it can just be an artefact of the Boltzmann brain, a file in your memory that appeared randomly. So the only thing the Boltzmann brain has to do is to provide an experience of a single moment of time. This can be done, in principle, without organs and so on.

Let me reiterate, the Boltzmann brain concept is hard to wrap one's head around because the moment it needs to create is not the one where you are first examining the concept, checking it for logical consistency, thinking about your past, checking whether you experience the passage of time etc. It only ever needs to create is an experience of now, the now that is happening as you finish reading the last word of this sentence.

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  • $\begingroup$ Does the thought experiment require a physical brain? If we replace the brain with an assembly of particles complex enough to generate memory or experience, is the thought experiment still valid? $\endgroup$
    – bassfocus
    Commented Feb 6, 2023 at 11:02
  • $\begingroup$ @bassfocus Yes, any assembly of particles complex enough to represent the experience of a mind at a given instant works. Of course, by allowing that possibility, you open yourself to a speculation as to what exactly should that assembly of particle look like. I.e., if we take a perfect scan of a brain and its chemical state, does the data file of that scan amount to a Boltzmann brain? That is, what is the difference between the representation of conscience and conscience itself? Of course, this question would be more appropriate for a different website. $\endgroup$
    – Void
    Commented Feb 6, 2023 at 11:58

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