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[Comments] (1) : I hadn't heard about Boltzmann brains before reading this NYT article, but I knew vaguely that inflation was making cosmologists come up with strange ideas. It's a great idea, and one that deserves to be explored in fiction, but I don't understand why a Boltzmann brain is supposed to be more likely than an orderly universe containing billions of real brains. If I'm reading it right, a Boltzmann brain and a universe are both possible results of a random fluctuation in the meta-universe. But a Boltzmann brain is very complicated and a universe is just a set of initial conditions. Basically I'm a computer programmer and the instructions for a universe that will eventually contain brains seem a lot simpler (therefore more likely) than the instructions for a brain. The universe is a lot larger than the brain, but if these things are budding off from the meta-universe I don't think our concepts of size are relevant.

Maybe a Boltzmann brain with my specific mental states is more likely than a universe containing a real brain with my specific mental states? As you can tell I don't understand this very well, but I just wrote 7 TF:AR entries (only 44 to go!) so I get to babble for a while. Maybe Kris has devoted some thought to the problem; it's the sort of creepy idea that would keep him awake.

Update: This weblog entry seems to be saying that I don't understand it because I don't believe the underlying argument about the structure of the universe. If I did believe that argument I'd understand Boltzmann brains, and then immediately agree that the whole thing was ridiculous and change my mind.


Posted by Kris Straub at Sun Jan 20 2008 17:23

It's super-tough once arguments dissolve into this kind of meta-solipsism. At that point, what arguments mean anything about anything? Although I guess it begs the question, why did we end up with this universe with this set of laws? Is it the most stable, easiest, simplest set? Couldn't we have had one that had more awesomeness, like where we could fly and punch buildings down and make up songs instantly? Is awesomeness innately more complex and energy-consuming?


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