Monday, July 27, 2009

More Boltzman Brain Problems

I was looking for new theoretical cosmology papers on today and saw there were a few on issues relating to Boltzmann Brains.

Basically here's the problem:
  1. There are, and always will be, only finitely many energy sources necessary to support the kind of intelligent life that progresses up through a long evolutionary path. (These sources are basically stars.)
  2. This means the number of such "real observers" has to be finite regardless of the age of the universe.
  3. De-Sitter space has thermal fluctuations that create a very small but non-zero probability that intelligent life will spring from the vacuum long enough to make an observation.
  4. Given our De-Sitter space seems it will expand forever, the number or Boltzmann brains will dwarf the number of "real observers" like irrationals dwarf rational numbers. (Let's leave countablity out of this, just needed some sort of analogy. Also, "real observers" are finite, unlike rational numbers.)
  5. Firstly, this is weird to think there should be more Bolzmann Brains that normal observers.
  6. Second, it is highly improbable if you are intelligent life that you are not a Bolzman brain, so given the life on our planet seems to be "real observers" we are a huge anomaly. Again weird.
Now, scientists don't like the above so some try to find ways of getting rid of Bolzman Brains. The papers today discussed things like the universe having a half life of 20 billion years with the de-Sitter space decaying. Then there is a cutoff where there isn't enough time for Bolzmann Brains to pop into existence.

Now, I don't do this kind of research since it is too crazy. But someone like me always gets a kick out of reading such papers. It's like science junk food that actually in some cases passes peer review. (However, in their defense, Bolzman Brains may someday be a technical hiccup that leads to important new physics.)

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