This post is just a copy of a thread over at Cosmic Variance. I’m copying it here because it’s an example of some of the mind-bending things that you come across in physics and mathematics, and one of the reasons that people do physics (and math). I’ve only read the post, so reading the thread should be interesting. Apparently Lee Smolin has written some comments on the thread, so it should be interesting. Lee, of course, is at the Perimeter Institute and is one of the high profile people looking at loop quantum gravity.
The thread starts here.
OO’s and BB’s
John at 3:02 am, February 21st, 2007
One nice thing about being a scientist, or at least an academic one, is that occaisionally you get your mind blown without any drugs or anything. Someone comes along and just pulls the rug completely out from under you – a total Denial of Reality Attack – and then you are left on your own to pick up the pieces.
Today at UC Davis we had a seminar from Don Page of the University of Alberta. The title and abstract of this talk sounded like science fiction, so I reproduce it here:
Don Page, University of Alberta
Title: Is Our Universe Decaying at an Astronomical Rate?
Abstract: Unless our universe is decaying at an astronomical rate (i.e., on the present cosmological timescale of Gigayears, rather than on the quantum recurrence timescale of googolplexes), it would apparently produce an infinite number of observers per comoving volume by thermal or vacuum fluctuations (Boltzmann brains). If the number of ordinary observers per comoving volume is finite, this scenario seems to imply zero likelihood for us to be ordinary observers and minuscule likelihoods for our actual observations. Hence, our observations suggest that this scenario is incorrect and that perhaps our universe is decaying at an astronomical rate.
Boltzmann brains? WTF? Intrigued, I went. This is a well-respected, highly-cited cosmologist after all. A former student of Stephen Hawking, no less. The jargon in the abstract, though bizarre, had a certain je ne sais quoi… Read the rest of this entry »