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PROBABILITY 1: Why There Must Be Intelligent Life in the Universe;\o7 By Amir D. Aczel\f7 ; \o7 (Harcourt Brace: 230 pp., $22)\f7

November 29, 1998|MARTIN GARDNER | Martin Gardner is the author of numerous books, most recently, "The Night Is Large," a collection of essays. His latest book is "Visitors from Oz," a fantasy novel

If one is on a hunt, it is better not to assume at the start that there is no game, or, you won't get what little there is.

--WILLIAM JAMES [in a 1902 letter]

*

The debate over whether there is intelligent life elsewhere in the universe is an ancient one. Greek and Roman atomists (Leucippus, Democritus, Epicurus, Lucretius) all defended a plurality of worlds. Plato and Aristotle thought otherwise. Medieval Christian thinkers, from Augustine to Aquinas, followed Aristotle and the Bible by confining mortal life to Earth. Pluralism revived during the Renaissance, notably in the writings of the German cardinal Nicholas of Cusa and the Italian ex-monk Giordano Bruno. (It is often said that Bruno was burned at the stake for his belief in many worlds, but it was mainly for other heresies.)

The Copernican revolution, which removed Earth from the center of the cosmos, surely played a role in the intense upwelling of pluralism in post-Renaissance centuries. Kant, Newton, Pope, Voltaire, Paine, Emerson, together with hundreds of writers and scientists, eagerly embraced the notion that intelligent life was everywhere, most likely on Mars, perhaps even on the moon. The leaders of America's two greatest Adventist movements--Joseph Smith, who started Mormonism, and Ellen White, founder and prophetess of the Seventh-day Adventists-- each defended a plurality of inhabited worlds. White, like the Swedish mystic Emanuel Swedenborg, even had visions of human-like beings on other planets. (Two eminent English exceptions to this belief were the naturalist Alfred Russel Wallace and philosopher of science William Whewell. Each argued strenuously against the possibility of extraterrestrial life.)

A widespread view among today's scientists is that the universe probably teems with life. There are billions of galaxies, each with billions of stars, and in recent years evidence has been increasing for a plenitude of other solar systems. So far only planets huge enough to cause detectable wobblings of their mother suns have been found, but there is every reason to believe that most suns, perhaps all suns, have planets of all sizes orbiting them.

In recent years, Carl Sagan was the most vocal scientist to trumpet a belief in the plurality of inhabited planets and to urge continual funding of searches for radio messages from extraterrestrial intelligence. Frank Tipler, a physicist at Tulane University, is Sagan's chief detractor. Tipler thinks the probability of extraterrestrials is zero and that listening for their signals is a big waste of time and money. Less aggressive skeptics include physicist John Wheeler, biologists Ernst Mayr and Jacques Monod, mathematician John Casti, astronomer Martin Rees and a raft of other scientists.

Amir D. Aczel, a statistician at Bentley College in Waltham, Mass., whose previous book, "Fermat's Last Theorem," won a 1996 Los Angeles Times Book Prize, is even more certain than Sagan that sentient life is not limited to Earth. In his new book, "Probability 1," as its title suggests, he maintains that the probability of beings on at least one other planet is so close to 1 as to be indistinguishable from certainty. Although his book covers the same ground as earlier books by others, there are two reasons for recommending it to any person interested in the debate: It is clearly and gracefully written, and it is up to date in its astronomical data.

In 1950, Aczel reminds us, the Italian physicist Enrico Fermi asked a famous question now called Fermi's paradox. The universe is so vast and so old, Fermi said, that if intelligent life is out there, we can expect many civilizations to have a technology far in advance of our own. Long ago they should have visited Earth. "Where are they?" Fermi asked. Because we have not seen them or heard from them, they probably don't exist. Like almost all scientists, Fermi dismissed UFO mania as popular superstition.

Many scientists refused to buy Fermi's argument. There are too many reasons, they said, why extraterrestrials would find it difficult to cover the vast distances between solar systems. Moreover, why would they select Earth from billions of other planets in our galaxy?

Aczel retells the story of how, in the late 1950s, physicist Philip Morrison, astronomer Frank Drake and others concluded that extraterrestrials might be sending messages using a certain frequency of radio waves. Drake's Project Ozma, named after the Princess of Oz in L. Frank Baum's popular Oz series, was the first attempt to listen for such messages using a radio telescope at Green Bank, W. Va. Others soon joined in the search. In 1993, a skeptical Congress stopped funding these searches. Drake, Aczel tells us, has continued his work with private funding from corporations. The most efficient search, SERENDIP III, is being conducted by Stuart Bowyer, using the world's largest radio telescope in Arecibo, Puerto Rico. Since 1992, it has examined 500 trillion signals without detecting a message.

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