The Great Silence – Milan Cirkovic ****

The great 20th century physicist Enrico Fermi didn’t say a lot about extraterrestrial life, but his one utterance on the subject has gone down in legend. He said ‘Where is everybody?’ Given the enormous size and age of the universe, and the basic Copernican principle that there’s nothing special about planet Earth, space should be teeming with aliens. Yet we see no evidence of them. That, in a nutshell, is Fermi’s paradox.

Not everyone agrees that Fermi’s paradox is a paradox. To some people, it’s far from obvious that ‘space should be teeming with aliens’, while UFO believers would scoff at the suggestion that ‘we see no evidence of them’. Even people who accept that both statements are true – including  a lot of professional scientists – don’t always lose sleep over Fermi’s paradox. That’s something that makes Milan Cirkovic see red, because he takes it very seriously indeed. In his own words, ‘it is the most complex multidisciplinary problem in contemporary science’.

He points out that the paradox is far more acute now than it was when Fermi formulated it, back in 1950. Based on a better understanding of galactic evolution, we know something no one suspected in those days – that most habitable planets are going to be billions of years older than the Earth. We’ve also discovered that life began to develop on Earth almost as soon as the planet reached the right temperature to support it. So there are stronger reasons than ever for supposing that ‘space should be teeming with aliens’. Yet, even with high-tech astronomical methods that were undreamed of in 1950, we still haven’t found a scrap of evidence for extraterrestrial civilisations.

After defining the problem, the bulk of the book is devoted to a detailed review of the many hypotheses that have been put forward to explain Fermi’s paradox. Some of them are fairly hackneyed, such as the ‘zoo hypothesis’ popular in science fiction, and various takes on the ‘rare Earth hypothesis’ – that there’s something intrinsically unique about our planet and/or our species (including, of course, the Bible-style ‘special creation hypothesis’). More thought-provoking are the ‘transcension hypothesis’ – that intelligent species evolve towards an energy-efficient post-biological form that is impossible for us to detect – and the ‘simulation hypothesis’, that the physical universe is an illusion, and we’re actually living in a computer simulation (amusingly illustrated in the book with a Dilbert cartoon).

But that’s just the tip of the iceberg – Cirkovic’s list goes on and on. I can’t help mentioning a few more (without even trying to explain them) just because I love the names he gives them: ‘Interstellar Containment’, ‘Thoughtfood Exhaustion’, ‘The Gigayear of Living Dangerously’, ‘Introvert Big Brother’ and ‘The Paranoid Style in Galactic Politics’ (if I was a sci-fi writer, those titles would keep me in business for several years). To bring some order to the chaos he follows the discussion with a (highly subjective) scorecard – giving his highest rating, A minus, to a variant of the rare-Earth hypothesis called ‘Gaia Window’ (for what it’s worth, this reviewer’s favourite, the transcension hypothesis, gets a respectable B minus).

There’s one little fact I’ve been holding back to the end. Cirkovic is a professional philosopher of science, and like all philosophers he’s extremely precise and meticulous in the way he uses language (a less charitable person would say he’s pedantic). That means it’s not the lightest of reads – although it’s not overly academic, either, as you can see from the phrases quoted in the previous paragraph. If you’ve already read a few books about the search for extraterrestrial intelligence, and you’re looking for something a little deeper, then this would be a great book for you. On the other hand, if you’re new to the subject, there are probably better places to start, such as The Aliens are Coming.

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Review by Andrew May