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The Anthropic Fallacy

December 1, 2009 5 comments

A couple of years ago, I attended a public lecture in Oxford given by Paul Davies, a professor of physics at various universities, including those of Queensland. and Arizona. He was on a lecture tour to promote his new book The Goldilocks Enigma, which addresses what appears to be a weirdly coincidental conundrum: that the universe – and planet Earth in particular – appears to be ‘just right’ for life to develop.

This claim is a variation on what is commonly known as The Anthropic Principle, and it has several real problems with it that classify it as an appeal to mysticism – the kind of populist tactic that has won Davies a lot of money from The Templeton Foundation. (The foundation makes a ridiculous attempt to unify science and religion, essentially bribing scientists to make vague religious claims for a million dollars.)

The core of Davies’s argument goes like this. The entire physics of the universe is based upon the values of only a handful of physical constants: things like the gravitational constant, the charge on the electron, the Plank constant, etc. This much is not in any doubt. If you were to change any of these constants, then the resulting physics would look different to how we see things in our universe, with our particular values for these constants. For some values, atoms would never form, making life as we know it (Jim) impossible, and in some, large molecules could never form, again stopping us from ever existing.

Look at our planet too – it’s just the right distance from the Sun to have liquid water on it, which appears to be essential for all the life we’ve so far discovered on it. Much further away, and we’d be frozen like Mars; much closer and we’d be roasted like Venus. Earth is in ‘The Goldilocks Zone’ – it’s just right for life. It also has an iron core, which gives it a magnetic field. This field deflects the high-energy solar particles, and stops them stripping away our atmosphere and our water. Perfect.

All these coincidences are adding up, aren’t they, and it’s tempting to stop for a moment and suspect that we’re a little bit special – the carefully prepared product of some guiding hand, perhaps…

But you’ve already probably spotted at least one of the problems with this kind of argument. Here are just a few:

  1. All the life on this planet is related – you only have to glance at the molecular evidence in the form of DNA. It’s all from the same stock, and is supported by the element carbon. We know of no other form of life, although some have suggested that silicon could possibly form the kind of complex, long-chain molecules that life needs, as carbon does. This tends to give us what is known as ‘carbon chauvinism’, in that there could be plenty of other intelligent beings that aren’t like us, and don’t require the kind of physical or chemical set-up we have here. Just because we don’t know about them doesn’t mean that they couldn’t exist.
  2. Hindsight gives a very illusory idea of cause and effect. Imagine you’ve hit a golf ball 300 yards and it comes to rest with a specific and unique alignment with the blades of grass it finally comes into contact with, as it inevitably must. The chances of exactly that configuration occurring is zero, considering the infinite number of alternative positions that the ball could have occupied. That doesn’t mean that it can’t have happened, though, or that it was somehow ‘planned’ because the ball has to end up somewhere, doesn’t it. It’s next to impossible to win the lottery, but someone does, and the fact that you couldn’t have predicted the winner beforehand (unfortunately) is just as much as a giveaway as the fact that you couldn’t have predicted the arrangement of grass blades on your golf ball after the drive.
  3. This brings us to the third point, which is that you couldn’t predict – and no computer simulations have done so, because the number of variables is far too large – what kind of universe you would end up with given any set of values for these universal constants. Even our own. So given a set of random values for the constants, we might possibly ‘end up with’ a universe, planet or life-forms that differ from our own, but who’s to say that a similar observation might not be made by the life-forms there, who might proclaim “Wow, this super weak charge on the electron is exactly what’s required for my kind of plasmoid energy-field life matrix.”
  4. There is also the sheer power of evolution to contend with when we come to alternative universes. Natural selection is a universal phenomenon, and it will operate in any situation where information can replicate itself, compete for population space, and pass on its characteristics (notably those that make it good at replicating itself). For life on Earth, that information is coded in the form of chains of atoms in DNA. Given a range of values for the universal constants, natural selection will operate to generate populations of replicators (that we may call ‘life’) that are better and better adapted to the niches in which the  individuals reside. Evolution will tailor life to fit the prevailing conditions, whatever they are, even in universes whose values for the constants might seem wildly exotic to us. Even in the presence of supercomputers that could work out the physics, this fact alone would mitigate against the possibility of predicting the kind of life that might arise.

I like to quote Douglas Adams when talking about the absurdity of the Anthropic Principle, especially in relation to the biological process that fits life to its environment:

Imagine a puddle waking up one morning and thinking, ‘This is an interesting world I find myself in, an interesting hole I find myself in, fits me rather neatly, doesn’t it? In fact it fits me staggeringly well, must have been made to have me in it!’ This is such a powerful idea that as the sun rises in the sky and the air heats up and as, gradually, the puddle gets smaller and smaller, it’s still frantically hanging on to the notion that everything’s going to be alright, because this world was meant to have him in it, was built to have him in it; so the moment he disappears catches him rather by surprise. I think this may be something we need to be on the watch out for.