# Centrepieces

## Carl Sagan's Universe

Edited by:
Cambridge University Press: 1997. Pp. 282 £40, $59.95, (hbk); £14.95,$22.95 (pbk)
Carl Sagan: tried to find life on other planets and to preserve the environment of our own. Credit: IAN RIDPATH

“The unifying theme of this symposium is the search for life elsewhere and the enhancement of life here. That captures the essence of Carl Sagan.” Bruce Murray's words set the stage for Carl Sagan's Universe, the proceedings of a meeting organized in October 1994 to celebrate Sagan's achievements on the occasion of his sixtieth birthday (and two years before he died). The result is a collection of articles that reflect the unifying diversity of Sagan's interests.

The search for life in the Universe and for the origin of life on Earth is the backbone of the first half of the book. It provides a concise, often historical overview of the American and (former) Soviet space exploration programmes, and then a more general discussion of the conditions required for the development and maintenance of life.

Most of the articles are very well written and include good illustrations (particularly some early and rare pictures of Mars). Appropriate emphasis is given to the evolution of the environments of the Earth-like planets and to the role of comet and asteroid impacts, either for the delivery of biogenic elements or as planet-sterilizing events.

The importance of perspective and context in space exploration — one of Sagan's favourite themes — is stressed in several chapters, bearing in mind its limitations. Would yet-to-be-discovered microfossils on Mars represent a separate martian origin of life, or would they instead suggest the inoculation of Mars by the Earth and/or the exchange of living organisms between the two worlds?

This first section reads essentially as a novel, and will be greatly enjoyed by both the planetary scientist — who will find in a concise, accurate and systematic form all the elements he already more or less knows — and the more general reader. The search for life then extends beyond the Solar System with a detailed historical and technical description of the search for extraterrestrial intelligence. There is then a (very difficult, not surprisingly) chapter on interstellar travel and time travel.

Science has shaped our world, not only through medical and technological revolutions, but also through its relationships with most human activities, including politics, power, education, communication and religion. The second part of Carl Sagan's Universe deals in depth with these interactions and illustrates the role of science as middle-man in this multiplicity.

For centuries, religion and science have been, and still are to a large extent, unmerciful competitors. One of the most important achievements of science has been to challenge the concept of the centrality of mankind.

Sagan, in his own chapter, recalls that this idea of man being at the centre of the Universe and unique as a species was not only inherited from religious or philosophical teaching in Western civilizations, but is also a founding principle of most cultures. But this ‘implicit’ belief has been defied by science: astronomy has shown that the Sun is in “the obscure outskirts of an ordinary galaxy” and that other stars appear to have planets, and biology has shown that humans share some 99.6 per cent of their active genes with chimpanzees.

Joan Campbell has another way of looking at this, saying that “science offers facts for men and women of faith”. Referring to the 1990 “Joint Appeal by Religion and Science for the Environment”, she notes the common sense of awe and respect for the Universe shared by many scientists and those of faith, and suggests a partnership between science and religion aimed at preserving the Earth. This is all very well, but doesn't it look like an electoral alliance between two parties with remote positions?

Preserving the Earth was one of Sagan's great concerns. The book highlights his pioneering work on nuclear winter and its role in informing the public and decision-makers on the most important environmental questions.

On the issue of information, the talent of the speaker, the means of communication, and the general level of scientific education of the public are all crucial to success. Jon Lomberg's excellent chapter on the importance of the visual presentation of science reminded me of a public talk given by Sagan in 1991 outside the Division of Planetary Sciences meeting in Palo Alto, California. Sagan was describing the annual increase of the ozone hole over the South Pole. The region depleted in ozone was seen as an ugly, well-chosen brownish spot whose size varied with the seasonal and long-term variability of ozone. Each time the brown region reached a maximum a distressed shudder went through the audience.

The book also emphasizes the interactions of science, politics and power which, at the end of a century dominated by military and space confrontation and the arms race, are obviously very strong. But the authors express different opinions on the plausibility of eliminating the nuclear danger from the world. The relationships between science and art are also briefly touched upon, but not too convincingly. Is it really science that influences art, or rather the object of science, that is, nature?

The general impression left by Carl Sagan's Universe is that, if mankind has not been given any centrality (only the merits of his actions, as Sagan says, may sometimes give him a justified feeling of importance), then science has certainly become central to mankind. Ann Druyan wonders whether democracy can exist without science.

The question raises the issue of whether, as science improves, it should be applied to encompass all aspects of human life. Sagan once proposed a position on abortion based on a purely scientific approach. His argument was logical and perfectly defensible, but is it the right approach to the problem? What about a scientific analysis of love, emotions, freedom or ethical behaviour? Regrettably, these issues are not addressed in the book.

Yet Carl Sagan's Universe, through the diversity of its contents and the generally high standard of its articles, remains a very fine piece of work that will interest a wide range of readers.

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