(1998) Amir Aczel, Little Brown, £17.50, hrdbk, 230pp, ISBN 0-316-64829-9
Though I've read many books on the probability of alien intelligence, this is the first I've read by a statistician. Unfortunately it is also one of the worst. Starting with the Drake equation, an assessment of the probabilty of alien intelligence using various terms such as rate of star formation etc., Aczel runs us briefly through the values of the 'known' parts. This is followed by a look at statistics, and how they are used, and Aczel himself warns how one must ask a question correctly in order for the analysis to afford relevent data. He then ignores his own warning.
Firstly, though he starts to use the Drake equation (which, depending on the values of the later terms, should give a rough assessment of how many alien races there are and, therefore, given a mean distribution of population density, how far away the nearest ones are), he abandons it half way through in order to arrive at the assessment of merely whether or not intelligent life can exist in the universe. Perhaps unsurprisingly, given the title, the probability is 1, ie. a certainty. Unfortunately this is very close to the strong version of the anthropic cosmological principle: we know intelligent life can exist, because we are here. The existence of humanity therefore satisfies the criteria, and no other alien races need exist.
Secondly, you have to backtrack the reasoning in order to discover Aczel's fatal error. It is basically this: he assumes that the removal of ourselves, or rather our sun, from the equation does not significantly alter the outcome. Indeed, he comes perilously close to stating that the reason there must be intelligent life in the universe is that the numbers at the beginning of the Drake equation are so huge that, no matter how small you make the subsequent terms, you will arrive at a number greater than 1. This works both ways, however, so if you include us 'in', we do not significantly affect the outcome, other than that we satisfy the contention that intelligence must exist in the universe. Therefore Aczel has taken 230 pages to prove nothing at all.
Basically he got lost along the way, and totally misunderstood the reason for the Drake equation. We already know that the probability of intelligent life in the universe is one, we ourselves are testimony to that. What we hope to discover through the Drake equation is how many intelligent lifeforms exist in the universe in total. This is a figure, not a probability, though probabilistic reasoning is used to determine the figure.
This book is an utter waste of time. Save your money.
Tony Chester
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