Rare Earth: Why Complex Life Is Unknown in the Universe [Anglais] [Relié]

"Do you feel lucky? Well do ya?" asked Dirty Harry. Paleontologist Peter Ward and astronomer Donald Brownlee think all of us should feel lucky. Their rare Earth hypothesis predicts that while simple, microbial life will be very widespread in the universe, complex animal or plant life will be extremely rare. Ward and Brownlee admit that "It is very difficult to do statistics with an N of 1. But in our defense, we have staked out a position rarely articulated but increasingly accepted by many astrobiologists."

Their new science

is the field of biology ratcheted up to encompass not just life on Earth but also life beyond Earth. It forces us to reconsider the life of our planet as but a single example of how life might work, rather than as the only example.

The revolution in astrobiology during the 1990s was twofold. First, scientists grew to appreciate how incredibly robust microbial life can be, found in the superheated water of deep-sea vents, pools of acid, or even within the crust of the Earth itself. The chance of finding such simple life on other bodies in our solar system has never seemed more realistic. But second, scientists have begun to appreciate how many unusual factors have cooperated to make Earth a congenial home for animal life: Jupiter's stable orbit, the presence of the Moon, plate tectonics, just the right amount of water, the right position in the right sort of galaxy. Ward and Brownlee make a convincing if depressing case for their hypothesis, undermining the principle of mediocrity (or, "Earth isn't all that special") that has ruled astronomy since Copernicus. --Mary Ellen Curtin

Renowned paleontologist Ward (Univ. of Washington), who has authored numerous books and articles, and Brownlee, a noted astronomer who has also researched extraterrestrial materials, combine their interests, research, and collaborative thoughts to present a startling new hypothesis: bacterial life forms may be in many galaxies, but complex life forms, like those that have evolved on Earth, are rare in the universe. Ward and Brownlee attribute Earth's evolutionary achievements to the following critical factors: our optimal distance from the sun, the positive effects of the moon's gravity on our climate, plate tectonics and continental drift, the right types of metals and elements, ample liquid water, maintainance of the correct amount of internal heat to keep surface temperatures within a habitable range, and a gaseous planet the size of Jupiter to shield Earth from catastrophic meteoric bombardment. Arguing that complex life is a rare event in the universe, this compelling book magnifies the significanceAand tragedyAof species extinction. Highly recommended for all public and academic libraries.AGloria Maxwell, Penn Valley Community Coll. Lib., Kansas City
Copyright 1999 Reed Business Information, Inc.

". . . [a book that] has hit the world of astrobiologists like a killer asteroid . . ." --Ce texte fait référence à l'édition Broché .

"Unlike many scientists who think that intelligent life may be abundant in the universe, Ward and Brownlee contend that any life found on other planets is most likely to be primitive--microbes or their equivalents. They advance what they call the Rare Earth Hypothesis, holding that Earth is probably rare among planets in orbiting a star that has had a fairly constant output of energy for billions of years and in being "of suitable size, chemical composition, and distance from the sun to enable life to thrive." Primitive organisms thrive on Earth in such harsh environments as hydrothermal vents, the authors note, and harsh conditions are likely to be the norm on other planets able to support any kind of life. Ward and Brownlee are at the University of Washington, where Ward is professor of geological sciences and zoology and Brownlee is professor of astronomy. Although simple life is probably abundant in the universe, they say, "complex life--animals and higher plants-! -is likely to be far more rare than is commonly assumed."

"If they are right it could be time to reverse a process that has been going on since Copernicus."

What is the possibility of complex life existing beyond our planet? What determines whether complex life will arise on a planet? How frequent is life in the Universe? In this exciting new book, distinguished paleontologist Peter D. Ward and noted astronomer Donald Brownlee team up to give us a fascinating synthesis of what's now known about the rise of life on Earth and how it sheds light on possibilities for organic life forms elsewhere in the Universe. Life, Ward and Brownlee assert, is paradoxically both very common and almost nowhere. The conditions that foster the beginnings of life in our galaxy are plentiful. But contrary to the usual assumption that if alien life exists, it's bound to be intelligent, the authors contend that the kind of complex life we find on Earth is unlikely to exist anywhere else; indeed it is probably unique to our planet. With broad expertise and wonderful descriptive imagery, the authors give us a compelling argument, a splendid introduction to the emerging field of astrobiology, and a lively discussion of the remarkable findings that are being generated by new research.

We learn not only about the extraordinary creatures living in conditions once though inimical to life and the latest evidence of early life on Earth, but also about the discoveries of extrasolar planets, the parts Jupiter and the Moon have played in our survival, and even the crucial role of continental drift in our existence. Insightful, well-written, and at the cutting edge of modern scientific investigation, Rare Earth should interest anyone who wants to know about life elsewhere and gain a fresh perspective on life at home which, if the authors are right, is even more precious than we may ever have imagined.

Offers a fresh and accurate perspective on the most profound question in science - I intelligent life in the Galaxy a dime-a-dozen occurrence or is it a cosmic fluke here on Earth? DLC: Life on other planets.

Peter D. Ward is Professor of Geological Sciences and Curator of Paleontology at the University of Washington in Seattle. His previous books include Time Machines and The Call of Distant Mammoths, The End of Evolution and On Methuselah's Trail, and, with Donald Brownlee, The Life and Death of Planet Earth. A member of the National Academy of Sciences, Donald Brownlee is Professor of Astronomy at the University of Washington in Seattle. He has been a member of numerous important NASA teams, and specializes in the study of the Solar System's origin, comets and meteorites, and the underlying subject of this book, astrobiology.