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Review of The Privileged Planet

David Hughes writing at The Royal Astronomical Society

We all had the Copernican Principle drummed into us at university. This paradigm insists that there is absolutely nothing special about the Earth. Its composition, physical characteristics, biotic activity, position, the star it is orbiting, its place in the Galaxy, the Galaxy itself, and the Galaxy’s position in the Universe are all supposedly unexceptional. Gonzalez and Richards disagree. Their thesis is that Earth is very, very special. To them, Earth is exquisitely fitted not only to harbour life but also to provide that life with a grandstand view of the surrounding Universe. Earth’s orbit, atmosphere, mass, rate of continental drift, dynamo-produced magnetic field, and companion Moon have been fine tuned just for us.

Ordinariness led Carl Sagan to predict from the Drake equation that the present-day number, N, of advanced civilizations in every Milky-Way-type galaxy was about 1 000 000. If, however, we are privileged, and special, this number plummets. Gonzalez and Richards suggest that N = 0∙01. We should begin to feel very lonely.

The Privileged Planet is pacey, informative, thought provoking, contentious, well referenced, and extremely hard to put down. Much is made of the strictures of circumstellar habitable zones, the weak anthropic principle, the importance of high metallicity for stars with planetary systems, the asteroidal threat and its relationship to the existence and growth rate of Jupiter, and the fine tuning of the important physical constants that is needed for life to originate and evolve. The basic tenets of the Copernican Principle are criticized. As soon as the Hertzsprung-Russell diagram and the stellar mass-luminosity diagram became well populated, astronomers realized that the Sun was far from being an ordinary star. As soon as the list of exoplanetary systems became respectably long we realized that our Solar System was way off the median. As soon as we started to make detailed investigations of the surfaces of our planetary neighbours we realized that life was rare. And things can easily get worse. What if the little bit of the Universe that we can see is completely dissimilar to the rest. Maybe it really is RIP for the Copernican Principle. Read this book. You will enjoy it.

Review: The Privileged Planet: How Our Place in the Cosmos is Designed for Discovery, by G. Gonzalez & J.W. Richards, (Regnery, Washington, DC), 2004. Pp. 444, 23∙5 x 16 cm. Price ₤18∙99/$27∙95 (hardbound: ISBN 0 895 26065 4).