Raphael Bousso (Berkeley) surprised me in the Physics Colloquium by saying some things about the anthropic principle that were not wrong. This is surprisingly rare. My principal objection to the principle is that there is no functional
we can apply to a theory and determine the existence of or density of observers
. I have secondary objections relating to whether it is observers we mean at all! But most talks we have had at NYU make an even more basic mistake, which is that of not clearly distinguising the need for observers from the observational matter that there are observers of the human type in our Universe. If you use the anthropic principle, ask yourself this: How does your anthropic
constraint on your theory differ from an observational constraint that the observed Universe contains, say, galaxies or structure or carbon or metals or stars or people?
The fact that the Universe contains observers of our type is an observation, not a principle. The fact that any observed Universe must contain observers may qualify as a principle.
In related news, Bousso also gave a very nice argument about the cosmological constant problem, which I had not appreciated. You might think that lambda (plus vacuum energy corrections) gets set to exactly zero at the big bang by some requirement on cosmological initial conditions. That's a good idea! But then at the electroweak phase transition, the vacuum energy density drops by an amount that is some 50 or 60 orders of magnitude larger than the currently observed value for lambda. So if it is a fine-tuning that is performed by the Universe, it must be fine-tuned before electroweak to a value that makes it very close to zero after electroweak. Nice demolition, that! He had various other good arguments for the problem being a very serious problem, and proceeded to use these issues to motivate an anthropic selection from the string landscape.
I spent the afternoon in-between meetings trying to plan my sabbatical next semester. It is important that the entire time go to research.
My principal objection to the principle is that there is no functional we can apply to a theory and determine the existence of or density of observers.
ReplyDeleteI disagree with this for this reason, but maybe you can find and correct some error in my thinking.
I have secondary objections relating to whether it is observers we mean at all! But most talks we have had at NYU make an even more basic mistake, which is that of not clearly distinguising the need for observers from the observational matter that there are observers of the human type in our Universe. If you use the anthropic principle, ask yourself this: How does your anthropic constraint on your theory differ from an observational constraint that the observed Universe contains, say, galaxies or structure or carbon or metals or stars or people?
Not that I don't have such a constraint, but this involves , so again, I would refer to the highly pointed nature of the Goldilocks Enigma, which does not ultimately point at "galaxies or structure or carbon or metals or stars".
The fact that any observed Universe must contain observers may qualify as a principle.
Give me a break, that's just a copout on the natural expectation for a dynamical structure principle that derives the configuration of our universe from first principles.
Man, I hate it when blogger.com screws up the code. It seems to happen every time I include more than one into the text. The sentence was supposed to read like this:
ReplyDeleteNot that I don't have such a constraint, but this involves "new" research... bla bla bla ... ...
So, did that help?... because I was getting a little concerned that you hadn't replied.
ReplyDelete