As I first learned at a dinner table surrounded by new acquaintances, questioning people's belief in extraterrestrial intelligence (ETI) is like questioning their religious faith. Doubts are met with gasps. The fierce stares say not just, "We disagree," but "You have blasphemed."
Don't get me wrong. I have nothing against curing cancer, heart disease, and AIDS, which advanced aliens could presumably do. I'd be fascinated to hear an alien's perspective on the meaning and purpose of life. I'm all for immediate solutions to our war/crime/ poverty problems, which a mature society is supposed to have solved. I even think that receiving all these blessings from above may follow logically from contact with a civilization that's survived for millions of years. But I also think that astronomers are now in a position to know that our chance of achieving such contact is very small.
Nothing drives ETI faith like the Copernican Principle, the idea that we do not occupy a privileged position in the universe. Many regard this as a necessary axiom for the continued success of the scientific enterprise. The practice of science begins, we are told, with the assumption that we are typical, not exceptional. We can't scientifically study a sampling of one, after all. Moreover, history suggests that Copernicus began an unstoppable progression: the world's greatest modern thinkers proposed and then proved that the Earth is not the center of the universe, that the Sun is not the center, that our galaxy is not the center, and finally, that there is no center.
Copernicus gave us the theory to take the first step, and Galileo demonstrated its truth. Einstein gave us the theory to take the last steps, and Edwin Hubble's observations of distant galaxies convinced the world.
Astronomer Robert Jastrow, founder of NASA's Goddard Institute, calls Hubble's achievement "the last great step in the revolution of thought regarding mankind's place in the cosmos that had been initiated by Copernicus." But today's Copernican Principle proposes, not only that the universe does not revolve around the Earth, but that the universe does not revolve around us, either literally or figuratively.
Having proved that our planet, sun, and galaxy are typical, science has yet to settle the question about whether we ourselves are typical. We lack absolute certainty that we are not, in the most important sense, the center--until someone confirms the existence of intelligent beings elsewhere in the universe.
Yes, if you put it that way, Robert Jastrow agrees: the final step in the Copernican revolution has yet to be taken. But in my talks with him during the 1990s, he insisted that we are on the verge of taking it.
"I think that mankind is on the threshold of entering a larger, cosmic community," he told me during a visit to his home and then to California's Mt. Wilson Observatories, where he serves as Director. His words carried a kind of ecclesiastical authority, seeming to reverberate from the seven-story dome above him, the observatory he calls a "cathedral dedicated to mankind's quest for understanding of the Cosmos." Less loftily, he added, simply, "We'll be hearing from those guys soon."
Taking a seat on the wicker chair that Edwin Hubble had sat upon almost eighty years before, I pondered this possibility--and then promptly forgot it while playing with the controls that split open the ceiling to the night sky, that slued the 100-ton telescope across the room, that spun the entire cavernous structure around me.
Sitting there a mile above Los Angeles at the focus of the world's largest telescope, positioned at the helm of the entire scientific enterprise, Hubble felt tremendous power. Oddly, he was simultaneously struck with a sensation of puniness, of being the first to fully understand how diminutive our place is in this enormous universe. While tweaking the controls over hundreds of cold nights through the early 1920s, Hubble provided photographic proof that our galaxy is but one of many. The nebulas, then understood to be wisps of gas among the Milky Way's stars, turned out to be more distant galaxies containing billions of stars of their own.
Now, having entered a new millennium, we're poised to make the final test of the Copernican Principle. And why should Robert Jastrow think our generation will be the lucky one to finally make contact, aside from the fact that his generation of astronomers can't die in peace until it happens? For one thing, new SETI (Search for Extra-Terrestrial Intelligence) telescopes and computers are being built with greatly enhanced sensitivity and coverage.
But Dr. Jastrow was thinking more about the signals we've been sending than those we hope to receive. "We're a very conspicuous part of the universe right now," he explained. "The TV and FM broadcasts--and the radar from our defense installations--are sending out a signal that there is life on this planet."
The SETI Institute's Robert Arnold agreed, saying: "These electromagnetic artifacts of daily commerce, entertainment, and defense give the Earth a distinct radio frequency signature that is brighter than the Sun."
According to Jastrow, "That started in intensity, at the million-watt level, about thirty years ago, in the 1960s." Jack Parr and I Love Lucy are at a wave front, he said, that's spreading out into the cosmos. "Within thirty light-years there are some dozens of stars. And if they got the word thirty years ago, they would be sending a reply back to us. And those who are only fifteen light-years away will have sent a message back fifteen years ago, which should just about be reaching us today."
Other astronomers belonging to Dr. Jastrow's generation recall the same kind of enthusiasm, but new concerns have since dampened it. "I used to rather enjoy thinking that the early civilizations would have set up an intercommunicating system," said Senior Astronomer Emeritus Eric Carlson of Chicago's Adler Planetarium. "Maybe laser beams or something full of information about all the other civilizations in the past history of the galaxy, and that this is all circulating ... from star to star around the galaxy, and all we have to do is tap into it."
The actual likelihood that we'll hear back from anyone that close, of course, depends upon just how densely packed our galaxy is with civilizations--and upon how long those civilizations last. Today Carlson frets about what might happen to any civilization in the course of a ten-billion-year-old galaxy. What will be left of human culture in a billion years, or even a million? "I tend to get this sense of a galaxy as being sort of like a garden," says Carlson. "You have the early spring flowers, and then you have the late spring flowers and so on, and you have life with consciousness springing up here and there for a while. And whether it's ever in contact at the same time, I just don't know."
The next generation of cosmologists might still say that the existence of extraterrestrial civilizations is "extremely likely," as cosmologist George Smoot (Lawrence Berkeley Laboratories) told me. "But I think the chances of there being life near to us is pretty low," he cautioned, "and whether there's life in our own galaxy, besides ourselves, I don't know."
Among the youngest astronomers to make a name for himself is Charles Steidel, the Caltech leader of an international team to discover ways of viewing thirteen-billion-year-old baby galaxies. His thoughts reflect the addition of twenty-first-century biological understanding to the equation: "The chance of there being life with which we would be capable of communicating, I think, is fairly low, because there are so many ways that things could develop."
Even Robert Jastrow, who has proved more relentlessly upbeat about alien civilizations than any other astronomer with whom I've spoken, appears to have had some second thoughts. When I was about to go to press with a book on modern cosmology, he asked me to make a small addition to a statement he had made in my chapter about SETI. Instead of saying, `We'll be hearing from those guys soon," he wanted me to change it to, "If lip ia common, we'll be hearing from those guys soon."
Most people are oblivious to recent evidence bearing upon the ETI question, both pro and con. But the Copernican principle is firmly embedded in popular culture, understood in terms of "the awful waste of space" if aliens aren't out there. Any chatty taxi driver can tell you that there are billions of galaxies and billions of stars within each. The sheer numbers demand that there be millions of habitable planets in our galaxy alone, even if the percentage of tenantable star systems is small. To say otherwise is to expose one's lack of scientific education.
Contact is assumed to be not a matter of if, but when. Our movies have given us progressively better special effects to prepare us for a day when the Earth will stand still, when we'll experience Close Encounters of the Third Kind, or when SETI will help us make Contact. Generation X and following have been entertained by more extraterrestrials than cowboys, Indians, and soldiers combined. It's probably not an overstatement to say that no movies have had greater influence on men under age thirty-five than the Star Wars films.
Infatuation with extraterrestrials further increased in the last decade. The Rockford Files became The X-Files. Mob-fighting Untouchables turned into alien-fighting Men in Black, also spun into a...