Boltzman Brains:

Certainly something funny going on with these Boltzman brains (BB) – looking for a thorough page  on these matters!

…. The idea Don put forward is this: there’s us, the ordinary observers (OO’s) in the world, who have achieved a certain stature after billions of years of evolution in the universe, and are now capable of making quite refined (or so we think) observations of the universe. …

Then, though, there are the BB’s in the universe: Boltzmann Brains. Random fluctuations of the fabric of spacetime itself which, most of the time, are rather insignificant puffs which evaporate immediately. But sometimes they stick around. More rarely, they are complex. Sometimes (very very rarely) they are really quite as complex as us human types. (Actually, “very very rarely” does not quite convey just how rare we are talking now.) And sometimes these vacuum quantum fluctuations attain the status of actual observers in the world. But, the rarest of them all, the BB’s, are able to (however briefly) make actual observations in the universe which are, in fact, “not erroneous” as Don Page put it.

The man was a compelling speaker, and soon I realized there was an actual intellectual debate underway in the high end of the cosmology/high energy community as to what the role of these BB’s might be in the universe, in the very far (or maybe not so far) future…

The thing is, when you start talking about very very…very rare things like Boltzmann Brains, you are talking about REALLY long times. Much longer than we’ve had on earth (and I mean 4.5 billion years) by many orders of magnitude. Numbers like 10 to the 60th years were being batted around like it was next week in this talk. By those times, all the stars and all the galaxies have gone out, and gone cold, and space has continued to expand exponentially and things are long past looking pretty bleak for the OO’s still around, who (we presume) need heat and light and at least a little energy of some sort to survive, even if we are talking about very slow machine intelligence (even slower than humans for example).

So eventually, the mere fact that there is, at these long times, just oodles of space in the universe means that the BB’s become more and more common (even if they are rare) and eventually dominate the, uh, intellectual landscape of the universe…

…I am mangling this horribly, and of course before writing this I took just a glimpse at the already voluminous amount of literature on this topic, and realized that I have a lot of reading to do, both blog and academic. So it’s best I stop and let you all go look up Boltzmann Brains, as I will, and do some more reading…

There’s a lot of time in a universe that’s open (expanding). Time enough for spacetime to dream the lives of mortals


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