I've just finished reading a book called "The Life of the Cosmos" by Lee Smolin. For those who don't know, Smolin is a theoretical physicist who is at the leading edge when it comes to theories of quantum gravity. He's come up with a very interesting idea, still very much conjectural, but one which is both testable and falsifiable.
Here's the Egg's attempted summary of the idea.
Observations
The universe we live in is incredibly fine-tuned, in terms of 20 to 40 physical constants (e.g ratio of proton to electron mass), which, even if they were slightly different, would make the universe a very different place and probably rule out any life altogether. (Smolin calculates the prob of this in the book at around 10^229 - no idea how he arrives at it)
General relativity predicts that the laws of physics (notably time) break down at a singularity. Quantum physics has nothing to say on this as we have no theory of quantum gravity. Yet.
Either time continues at a black hole or it doesn't. Lets say that (conjecture alert!) time continues ar a singularity in an otherwise inaccessible part of the universe. To somebody in this universe it might appear that at some point in the past the universe began with a singularity and may look indistinguishable, in the main, from our own universe and how we see it.
Here's the rub (conjecture alert no.2!), the physical constants which govern the universe, as mentioned above, are slightly altered at each singularity, so the laws of physics in that spacetime are slightly different.
It follows, that some of these universes will "fail", exist only for a fraction of whatever passes for time and "bounce" to form a new universe with slightly different parameters. Some universes will be devoid of matter. In fact the only thing you can say with any conviction is that....
Universes will tend to favour physical constants which produce the greatest number of black holes.
ie universes which produce black holes go on to produce black holes go on to produce black holes (assuming this physical constant shift is tiny)
(c.f survival of the fittest)
So how do we test this? Easy
, we work out whether changing the physical constants of the universe, either up or down make black holes more or less likely. (OK "likely" is not a v. scientific term). After all, its overwhelmingly probable that we live in a universe which is maxed or close to maxed its "black hole makeability".
If by changing 40 constants we found they all gave the chances of black holes as less likely, well what would be the chances of that? 2^40!! Mind you, the actual calculations aren't very easy at all and require a fair amount of calculated guesswork, but Smolin thinks he can demonstrate this without question for about six of the constants so far. It is still, however, a speculative and as yet controversial theory.
What I like about it is:
1) evolution by natural selection, the key driver for life on Earth, becomes the key driver for, well, everything.
2) all scientific discoveries seem to push humanity further away from the all important podium it had built for itself. Each discovery seems to make mankind's place in the universe just that little bit more humbling.
This idea, if true, means that the universe (or in this case multiverse) is mindbogglingly big (composed of up to 10^229 universes!). Sheesh!
Just wondered if anyone had heard of this conjecture or has any thoughts. Its described far better than I could, here:
Scientific theories and methods modelled on natural selection.
Or just do a google search for any number of book reviews.
Apologies if I've completely ballsed up the explanation btw, but I think all will agree its a damned intriguing prospect.
PE