17 October 2006

natural selection of universes !

Why is the universe the way it is - why are the fundamental properties of elementary particles and forces just such that complexity can arise? Shift the values of these fundamental properties around just a bit and things dont work out so well.. a universe with even slightly varying properties either doesnt survive very long or ends up very empty with no ability for complexity of any sort to arise.

The answer i've most liked so far is that we just happen to be in one universe (of an infinite set within a theoretical multiverse) that does allow for complexity, and that the other sorts of universes that form without the right properties dont exist for long and wont have anybody within them to ask any of these questions anyway..

but Lee Smolin's "natural selection of universes" idea is simply more beautiful and 'complete'. He starts of with the general postulate that some self organising cosmic scale phenomenon could underly the selection of fundamental quantum
properties, but where it gets really beautiful i think is his suggestion that that phenomenon is evolutionary - that universes have evolved fundamental properties that make their reproduction more likely.

As Martin Rees comments: "He's saying that in some sense the universes that allow complexity and evolution reproduce themselves more efficiently than other universes. The ensemble itself is thus evolving in some complicated way. Smolin speculates - as others, like Alan Guth, have also done - that inside a black hole it's possible for a small region to, as it were, sprout into a new universe. We don't see it, but it inflates into some new dimension"

To continue the metaphor he uses - universes as animals, fundamental physical properties as genes, and black-holes as reproduction events.

Read the Whole article here - it is a bit old and (in places) dated, but the underlying idea of natural selection for universes, seems to me -at least tonight- to be very exciting.

One question i do have with the article (and some of the comments) concerns the assumption he uses to conclude that the idea is testable - that any tweaking of fundamental properties should produce less or equal number of blackholes, but NOT more. According to Smolin, this should be the case because universes would have evolved to optimize their properties so as to have the maximum chances for reproduction.

But does our understanding of evolution bear this out? Evolution doesnt necessarily achieve perfection - it doesnt even strive for it - its just a self organizing phenomenon that allows things that can persist to persist. What i mean is that there is no guarantee that our current universes 'gene-set' is necessarily the most optimized..

If i'm right, this means that the testability of his theory is open to question - that if anyone finds a shift in fundamental values that allows for more blackholes, the whole theory is not necessarily proven wrong. Thats more sad than it sounds, because without testability, its just another beautiful idea.

(UPDATE: in the comments to this blog, someone pointed out that Smolin addresses this in his book, 'The Life of the Cosmos')

Something else that might be worth considering is the possibility of other 'reproduction events' that werent thought of when he wrote this - like maybe the "Brane collisions" that possibly create universes in some of the newer forms of the superstring/m-theory/membrane theories
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