Nature

Magazine Overview

This issue of Nature, dated 21 March 1996, features a cover story titled "Alone in the Universe?" which reviews two significant books on the topic of extraterrestrial intelligence (SETI).

Book Reviews

Extraterrestrial Intelligence by Jean Heidmann

Reviewed by Woodruff T. Sullivan III, this book is described as an excellent translation of the 1992 French original, aimed at the general public. It covers the field of exobiology (or bioastronomy) comprehensively, detailing the journey from the Big Bang to the origin and evolution of life, and then focusing on the nature of extraterrestrial intelligence and methods for searching for it. The review notes that while the book covers actual searches up to Project Phoenix, Serendip, and BETA, it lacks illustrations and exhibits a peculiar lack of editing for an international audience, with references to French scientific history (e.g., Baron Joseph Fourier).

Extraterrestrials: Where are They? Second Edition, edited by Ben Zuckerman and Michael H. Hart

This book stems from a 1978 symposium but has been expanded and revised in its second edition. Approximately half of the text is new. The chapters vary in technicality, with some being moderately technical and others more accessible to nonexperts. Topics covered include the origin of life, evolution, interstellar travel, colonization techniques, UFO debunking, and search strategies for SETI. The review highlights that the book's tenor is skeptical about the existence of extraterrestrial intelligence, though optimistic views are also presented.

Key Themes and Arguments

The Fermi Paradox

A central theme discussed is the Fermi paradox, which questions the apparent contradiction between the high probability of extraterrestrial civilizations existing and the lack of evidence for them. The paradox posits that if such civilizations were abundant, they would have likely colonized the galaxy by now.

Probability and Naivety

The evolutionary biologist Ernst Mayr is cited for arguing against the optimism of physicists and astronomers regarding SETI, suggesting their biological naivety has misled them. The difficulty in estimating the probability of other life forms is acknowledged due to having only one known example (Earth).

Cosmological Estimates

Cosmologist Richard Gott's use of the Copernican principle is mentioned to estimate that there could be up to 100 radio-transmitting civilizations in the Milky Way, implying that any detected neighbor would be relatively distant and require significantly powerful transmissions to be found.

Habitability Zones

The review notes that Hart's original argument on the habitability zone for planets around a star from a 1979 study has been updated by recent work that has widened the zone significantly.

Scientific Efforts and Future Outlook

The issue details various scientific efforts in the search for extraterrestrial intelligence, including radio searches, the Viking spacecraft's experiments on Mars, and ongoing projects like Phoenix, Serendip, and BETA. The review concludes by emphasizing that as our understanding of the Universe grows, so will the debates and research into the origin of life, extraterrestrial life, and intelligence. The discovery of planets orbiting other stars is noted as a spur to further scientific exploration.

Recurring Themes and Editorial Stance

The recurring theme is the persistent scientific inquiry into the existence of extraterrestrial intelligence, despite the lack of definitive proof. The editorial stance, as reflected in the book reviews, appears to be one of cautious skepticism tempered by the ongoing scientific exploration and the profound implications of the question "Could it be that we are not alone?" The magazine highlights the interdisciplinary nature of this field, drawing from astronomy, biology, and physics.