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


Anonymous said...

cool blog jaysen. i just read it again now


Anonymous said...
This comment has been removed by a blog administrator.
Unknown said...

Which leads us to ask how do they reproduce, and more importantly, does the galaxy have a gender, or is it asexual? Does it evolve by means of mating? How would it find a suitable partner?

Lends a whole new meaning to the Big Bang ;)

jaysen said...

a-man - as universes necessarily dont share the same space-time, dating becomes too difficult for sexual reproduction.

although, maybe the brane-collision hypothesis, which involves the collisions of two seperate spacetime membranes, is sort of sexual.

Fan Fan Hulmaida said...

Consider the set of possible organisms (or universes) that could evolve as distributed over a landscape, with simpler structures being lower down and more complex being higher up. The more unlikely, complex and organised structures are at peaks in the landscape. Dawkins is all about showing that every improbably sheer cliff is reachable by small, gradualistic, Darwinian changes in design. Attaining higher peaks tends to require some downhill walking towards more simplicity, at least initially. We would expect complex evolved items (like us and our universe) to be at local maximums (of reproductive fitness), islands of evolutionary stability, occasionally nudged towards greater heights of complexity by environmental change and variation.

Smolin's CNS seems attractive because the causal antecedent of the whole multiverse ensemble (i.e. the first big-bang big enough to produce a new black hole), need not possesses the unexplained complexity, structure and order of our current universe. This can arise naturally via CNS.

Perhaps this makes the original 'quantum fluctuation in the void' (that got the whole ensemble going) simple enough not to cry out for explanation like fine-tuned organisms and universes do, in which case the 'Argument from Design' is undone. If only CNS also resolved the cosmological question - 'why is there something rather than nothing?'

If these black-hole/big-bang domains are not forever causally distinct (as your faintly troubling 'mating universe' scenario implies), calling them 'universes' seems especially gratuitous. Anyone got a catchy name for our 'local space-time domain'? It will soon be relegated, just like Pluto...

jaysen said...

fan-fan: I like smolin's idea for those reasons too. Its just the claim of falsifiability that i'm having trouble with, because i think that any discovered higher local maximum could be explained as signs of random drifting mutation along the beach of such islands of evolutionary stability. Therefore, such a discovery would not necessarily prove the theory false - even, i think, by the standards of probabilistic falsifiability.

as for the 'mating universes', i was being slightly cheeky, but is a universe spawned by a black hole also 'forever causally distinct' from the universe that contains the blackhole?

Fan Fan Hulmaida said...

If there are a range of independent constants which affect the number and distribution of black holes (and that is a big 'if') then CNS predicts that they would tend to be at local maxima for black hole production. If any particular one were found to be far from this value, falsification of CNS might be avoided by invoking random drift. However, this strategy is not going to work for the whole set of constants. If the values of these constants are randomly distributed, with no clear trend towards black hole fecundity, then this form of CNS is falsified. Smolin spells it out quite well in his book 'The Life of the Cosmos'.

As for the causal distinctness issue, this may just be semantic. The standard account of 'universe' is 'all that there is'. A remodeling in light of Smolin's, Vilenkin's, Tegmark's, or Everett's physics treats 'universe' as 'distinct causal space-time domain', with the suggestion being that if two domains can interact causally, they must be part of the same universe. I guess my ideas about causality find no purchase when we talk about events in one space and time causing events in another space and time - I am no longer clear on the modus operandi.

Whether a black hole can interact with its parent might depend on whether the information lost to a black hole is retrievable in the long term.

Anyway, the best part of Smolin's work is charting the organic, almost biological nature of the evolution of galaxies.

jaysen said...

fair enough - will have to find and read 'The Life of the Cosmos'

Fan Fan Hulmaida said...

Here is something relevant:


Fan Fan Hulmaida said...

some more... http://video.stumbleupon.com/#p=anzobm3cps

jaysen said...

thanks fan-fan. Still havent got my hands on Life Of The Cosmos - might have to wait till i leave Algeria in 8 months, for lands better served by amazon