If E.T. exists, there's no evicence -- yet


"Other Worlds: The Search for Life in the Universe," by Michael D. Lemonick. Simon & Schuster. 352 pages. $25. Are we alone in the universe? As of now, the answer is unequivocal. There are no aliens orbiting the earth or living among us. E. T. has not phoned in from some other solar system. There is no evidence that any sort of life exists anywhere but on our earth.

Yet this answer comes with a crucial qualification: We've never actually seen any of the places outside our solar system where life might be found. As Michael Lemonick, a science writer at Time magazine, explains in his lucid and intriguing survey of ongoing work on this issue, there are good reasons to believe that other technologically advanced civilizations exist elsewhere in the universe.

The key to this claim lies in something called the "Drake Equation." Named after the radio astronomer who devised it, this equation is actually simpler than the average tax return. It says that "N," the number of technologically advanced civilizations in the universe, is equal to the number of hospitable planets times the proportion of those planets where life arose times the proportion where civilization arose times the proportion of worlds where such civilizations currently survive. Because we exist, we know that "N" is at least one. "Other Worlds" describes what scientists are doing to push "N" from one to two.

The only certain way to change that number is to discover a non-terrestrial civilization. At present, Lemonick makes clear, the hopes for doing so are slim. There are no telescopes capable of sighting a planet - even a planet as large as Jupiter- orbiting even the nearest neighboring star. The SETI (Search for Extraterrestrial Intelligence) Institute has a 140-foot diameter radio telescope listening for transmissions from nearby stars. But even though that telescope could "pick up a cellular phone operating on Pluto" it is probably not powerful enough to hear something like a television signal from a star eight to 10 light years away.

Because of such limitations, most of the research that "Other Worlds" describes is aimed at improving estimated values for one or another term in the Drake Equation. Specifically, this means building better instruments, hunting for evidence of planets orbiting other suns, and looking for signs of life on other worlds in our own solar system.

All three lines of investigation, Lemonick reports, are producing results. Lemonick's account of these works in progress is more a recitation of possibilities than a critical discussion of results. But the advances he describes make it seem likely that we will someday find life in another solar system. And that, many scientifically inclined readers would agree, could be the greatest discovery mankind has ever made.

John R. Alden is an archaeologist whose research has focused on the origins and evolution of complex societies. He has done fieldwork in northern Chile, Mesoamerica and the Middle East. He has also written two travel articles on Chile's Atacama Desert and the Florida Everglades, for the New York Times.

Pub Date: 5/10/98

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