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Life in the universal porridge

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What were the chances that the conditions in the Universe would be just right for life?

The Goldilocks Enigma: Why Is the Universe Just Right for Life?

Paul Davies Allen Lane: 2006. 360 pp. £22 0713998830 0618592261 To be published in the US in April as Cosmic Jackpot (Houghton Mifflin).

The Hitchhiker's Guide to the Galaxy asked about Life, the Universe and Everything. Credit: TOUCHSTONE/SPYGLASS ENTERTAINMENT/KOBAL COLLECTION

The biggest question of all, according to writer Douglas Adams, is the one about the meaning of Life, the Universe and Everything. Paul Davies, in his book The Goldilocks Enigma, phrases it as 'How come existence?', but it is the same age-old question, and we humans have taken several routes to try to answer it. The option preferred by most scientists is a cop-out: that we are just a cosmic accident, and that the Universe just happens to be right for life to have evolved in it. They argue that trying to find deeper meaning behind this incredibly unlikely outcome is futile, and hope that some as yet undiscovered laws of physics (such as may one day be provided by string theory or another 'theory of everything') will show us that things simply could not have been any different.

There is a second option. A growing band of physicists has argued that our universe is not unique but rather one of many within a larger Multiverse. Given the quite stupendous odds against us being here and the degree of fine-tuning in the laws of nature necessary for life to have evolved, it is not surprising that some have argued for the reality of multiple universes.

Here is a simple example showing how this helps. If millions of people buy lottery tickets, it is not surprising that the winning numbers should come up (maybe more than once). Of course, if your ticket contains those winning numbers, you might consider yourself incredibly lucky. But to anyone who doesn't know you, it is nothing remarkable; after all, someone has to win. Now let us suppose that in the week you bought your lottery ticket, no one else bought one, and yet you have the winning numbers. Is this now more remarkable? For you, there is no real difference, because the odds on you winning are the same whether anyone else buys a ticket or not. But from the point of view of the set of winning numbers, it is truly remarkable that they match the numbers on the only lottery ticket. This is the dilemma we face when we contemplate the incredibly tiny odds on our existence. We are those lottery numbers, and we need a lot of tickets to be bought if we are to stand a reasonable chance of matching anyone's ticket.

For years, the issue had been dismissed anthropically: if the conditions in our world were not 'just right', we wouldn't be around to debate the issue. However, it is much more natural and logical to conclude that even though we might be unique, our universe cannot be. If the Multiverse contains an infinite number of universes, some of them must have the right conditions for life. Can it really be that simple?

The first half of The Goldilocks Enigma is standard fare, covering all the usual topics, from the Big Bang, inflation and high-energy particle physics to theories of everything and where the laws of physics come from. Davies has a knack of making these subtle and complex concepts seem straightforward. But it is the second half of the book that readers will want to skip to. It is here that he faces head-on the question of why our universe is just right for us, and he covers all the main arguments thoroughly and shows up their shortcomings. Eventually, he chooses a different path that does away with luck as well as the Multiverse. But as Deep Thought, the computer in Douglas Adams' The Hitchhiker's Guide to the Galaxy, says, you are not going to like it.

Davies' first suggestion is that the 'biofriendliness' of the Universe may be due to some as yet undiscovered 'life principle', built into the laws of physics from the very beginning, that has steered and constrained the Universe towards producing life. I find this idea hard to swallow and I don't think Davies dwells on it long enough to really make a convincing case.

He then invites us to consider a more interesting — I hesitate to endorse it with the term 'appealing' — idea originally expounded by physicist John Wheeler. It takes one of the weirdest features of quantum mechanics and pushes it to its logical conclusion: that conscious observers bring about the universe they find themselves in by the very act of observing it, thereby dragging it out of the quantum superposition of all possible paths it could have followed. Actually, I think this is related to what supporters of the Multiverse version of quantum mechanics would argue — with the difference that, for Davies, our universe is the only one.

The main options, then, are: first, that the Universe is a fluke; second, that it is one of many and happens to be, much like Goldilocks' porridge, just right for us; and third, that conscious observers bring the universe they inhabit into existence simply by observing it, although their teleological actions would have to reach back into the past, forcing the right conditions to be selected at the Big Bang.

Just when the reader feels that Davies is losing his grip and sliding inexorably towards fantasy, he takes a well-timed reality check, reminding the reader, and himself, that in order to address the question of 'How come existence?', one must either play it safe and back away from the question, or be quite radical. Many physicists will not like this book, but I think it will cause the biggest stir since Roger Penrose wrote The Emperor's New Mind (Oxford University Press, 1989). Most of the ideas are not new, but Davies is courageous, entertaining and persuasive in laying them out clearly. Many scientists might feel that the subject matter, as Davies acknowledges, should be 'left to the philosophers and priests', with scientists tackling only those questions they can hope to answer. But it's still a thoroughly good read.

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https://doi.org/10.1038/444423a

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