The Betfair Prof / Leighton Vaughan Williams / 23 March 2009 / Leave a comment

Leighton Vaughan Williams has some mind-blowing thoughts on the chances of life establishing itself on planet earth.

Let's play a thought experiment and imagine we are standing outside the universe and taking bets on the likelihood of the universe starting up and creating intelligent life. Yes, it's a thought experiment in which we are constructing a sort of cosmic prediction market.

The first thing we notice is that if the constant of universal gravitation was different from what it happens to be by an almost unimaginably small amount, the game would be up. To achieve the level of precision required to get the show on the road by chance has been compared to the probability of randomly throwing a dart at a dartboard the size of the entire visible galaxy and hitting the bull's-eye!

But that's just for starters. A similar sort of mind-blowing improbability applies when considering a range of other variables. Take the size of the strong nuclear force which binds together the nucleus of the atom. A minute bit different and the show's over before it's begun. Same story for the mass of the neutron or the charge of the electron and so on and so on. I could go on listing the variables that need to be 'just right' but you get the general idea. In simple terms, it just ain't going to happen! No chemistry, no planets, no life.

But let's say for a moment that we throw all this reasoning out of the window and assume that all these vanishingly small probabilities combine to produce one giant universe. What then about the chance of intelligent life on our planet?

Some of the latest thinking is that all intelligent life can be traced to a single bacterium that developed the ability to use sunlight to break down water and liberate oxygen, about 2.2 billion years. At that level life would have remained, however, but for a unique encounter in which a descendant of this bacterium became engulfed and incorporated into the body of an amoeba-like organism that originally attacked it as prey. Without this single unprecedented event, estimated to have taken place more than 300 million years later, the conditions for the evolution of complex life forms could not have taken place and life would have stopped at the level of primitive organisms.

Two freak one-off events, in the 3.5 billion year history of life on Earth. So unlikely that scientific analysis suggests that neither has happened since. Once and once only, for each, in the 3.5 billon year span of life on earth.

Well, there are plenty of planets, and it may just be that ours got lucky, very lucky! Nice argument but doesn't really work at the macro-level. If there are billions of planets, we'd maybe expect some to produce life once given the chance. To claim the same at the level of the universe seems to mean assuming that there are billions of universes.

Some scientists have an answer and it's simple enough. There really are billions of universes, and our universe just got lucky. Well, why not extrapolate from that and say that there are an infinite number of universes? Which means that somewhere anything that can happen, has happened. And will happen, somewhere else. Over and over again. Ad infinitum. However cruel, however evil, we can count on it.

A terrifying thought, if you believe it. That's the problem with thought experiments about cosmic prediction markets. Sometimes they predict what we'd least like to be true. Of course, there's an alternative explanation. Maybe instead the universe, and life within it, is not a chance event, but (in the words of cosmologist Fred Hoyle) a 'put-up job'. What's the market price about that? Even money, you say? OK. I guess I'll take it!