Saturday, 31 March 2001

Amir Aczel: Probability 1: Why There Must be Intelligent Life in the Universe (1998)

Edition: Little, Brown & Co, 1999
Review number: 795

The question of the existence of extra-terrestrial life is one which has fascinated the human race since classical times. In recent years, various attempts have been made to estimate the likelihood that such life exists, prompted in some part by the popularity of science fiction. This sort of speculation begins with what is known as the Fermi paradox, which is basically that we should already know if there is intelligent life more advanced than we are because they should have contacted us already.

This way of looking at things actually suggests other questions, which are rather more interesting that whether life exists at all; it would be hard to get excited by a universe populated only by micro-organisms other than on our own planet. Basically, these other questions amount to speculation about what form putative extraterrestrial life might take - could there be advanced civilizations? How could we know? They actually lead back to close study of life on earth, to try to see how things could have developed differently.

There is an equation, the Drake equation, which predicts the likelihood of contact by an advanced alien race; this is put together by assigning probabilities and expected values to various events, most of which is guess work - the probable lifetime of a civilization, for example. Aczel's book, after a discussion of some of the issues raised in the previous paragraph, makes an estimate for the first few values in the equation, those which refer to the existence of life itself rather than levels of technology, and infers from this that the probability of life existing somewhere else in the universe is essentially indistinguishable from 1, certainty.

This is done through some elementary probability theory, which essentially amounts to saying that the universe is so big that, no matter how unlikely, life must exist somewhere. This is saved for the end, but much more interesting is Aczel's explanation of why he thinks humanity might well be the most mature civilization in the universe (as a result of the inspection paradox, unfortunately not as clearly explained as most of the mathematics in the book).

The book as a whole is not as successful as Aczel's earlier explanation of Fermat's Last Theorem, at least as far as I am concerned. A lot of it is over-simplified - I ended up skipping a lot of the early part of the book. It picks up in the middle, when nuggets of interesting information start to be included, but unfortunately becomes less interesting again as it starts to concentrate on the existence of life in general rather than intelligent life.

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