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Book Review:
Life On Other Worlds And How To Find It
by Stuart Clark (Praxis Publishing, ISBN 1-85233-097-X, 2000)

reviewed by H. Paul Shuch, Ph.D.
Executive Director, The SETI League Inc.
(n6tx @

PEOPLE are fascinated by the prospect of life in space. My proof? I count an even dozen volumes on bioastronomy on my bookshelf, all published with the past year. But among these, Stuart Clark's Life On Other Worlds and How To Find It is unique in its approach. We must walk before we run, says Clark. Don't even ask the age-old question "Are we alone?" until you've brushed up on the basics.

And these basics are the principles and assumptions that underlie any search for life beyond our sphere. Here, Clark invokes the writings of Carl Sagan, Paul Davies, David Blair, Christian de Duve and many other respected experts. A swift tutorial on cosmic evolution plus a smattering of basic thermodynamics takes us from the big bang to the formation of planets that might, just possibly, support life. This sets the stage for a lucid discussion of the emergence of life and exactly what constitutes a hospitable environment. The backdrop is a picture of Earth-like planets as commonplace among the myriad worlds in our Universe.

But just because life could exist elsewhere is no guarantee that it does. To find out, we have to do the experiment. We have to collect the data.

The search for life within our own Solar System has its roots in the 18th-century furore over supposed canals on Mars. Centuries later, the controversy continues, but now it is over the 1996 claim that a Martian meteorite contains microbial fossils. Exobiologists have not rejected the prospect of finding primitive life close to home. Several space missions are due to leave the drawing board and test for the presence of life.

Their search has also been given new impetus by the discovery of planets outside the Solar System, the first detected only five years ago. All these extrasolar planets are giants like Jupiter, but there are plans to launch space-based observatories capable of spotting Earth-sized planets and of identifying atmospheric gases conducive to--and perhaps even indicative of -- life.

But what will this life be like? Those involved in SETI, the search for extraterrestrial intelligence, hope to find intelligent, technologically advanced life rather than brainless bacteria. The more prevalent intelligence is, the greater will be our opportunity for contact. Clark has a crack at defining intelligence and pinning down the role it plays in evolution and survival.

The high spot for fans of SETI science will be the account of our efforts to communicate with aliens. In 1820, for example, Karl Gauss proposed creating a giant triangle of trees in Siberia to signal our mathematical prowess to our supposed lunar neighbours. Recent efforts have been more sophisticated. Clarke briefly mentions recent attempts to detect alien laser beacons, but, sadly, neglects to mention the pioneering Optical SETI work of british engineer Dr. Stuart Kingsley.

The problem of defining what constitutes proof is juxtaposed against public suspicions about hidden evidence and government cover-ups. As a false alarm recently showed, announcing to the world that we've found an alien signal may be a problem. And should we fear our Galactic neighbours? Controversy surrounds active SETI, the deliberate transmission of messages from Earth, for example.

Which brings us back to the well-worn Fermi paradox: where are they? Clark is convinced we are not alone. But if the extraterrestrials won't come to us, perhaps we'll have to go to them. That's the excuse for an entertaining rummage through the wilder reaches of technology: fusion rockets, solar sails, matter-antimatter reaction engines and lunar mining, not to mention self-replicating Van Neumann probes and instantaneous communication via quantum entangled particles.

However we find it, Clarke is certain we'll get there somehow--and that there's an abundance of extraterrestrial life. An astronomy educator by trade, he uses wit, humour and even the occasional Star Trek cliché to make his case. But this is not a speculative work, and Clark's personal conclusions are incidental to his broader picture. His finale as an eloquent justification for the continuation of SETI. "Only by the continued efforts and collaboration of the scientists, who approach the quest from their own unique vantage points, can we hope to find the answer to this, the most perplexing question of our anybody out there?" he writes.

Life On Other Worlds is visually spare, but it is rich in language and long on clarity. As a SETI professional, I kept a sharp eye out for any errors. I found only one, and a minor one at that. In discussing the signal detection hoax of October 1998, Clark says it was "an amateur radio astronomer who claimed to have picked up a message from the star EQ Pegasi, just 22 light years away". In fact, an anonymous Internet hacker, posing as an amateur radio astronomer, made that claim. The distinction is important, as amateur astronomers are disciplined and professional.

As an astronomer, Clark is well aware of the significant contributions of amateurs to his discipline. He speaks well and clearly to the educated non-scientist in Life On Other Worlds and How To Find It, an engaging and worthy read. Astronomer Patrick Moore, whose The Sky At Night is Planet Earth's longest-running television series, writes in the foreword, "in my view [this book] is the best of its kind that I have seen, and it will have an honoured place on my shelf."

I couldn't put it better myself.

This review first appeared as "Looking for Company" in New Scientist (2232): 48-49, 1 April 2000, and is copyright © 2000 by New Scientist; used by permission.

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