2008 : WHAT HAVE YOU CHANGED YOUR MIND ABOUT? WHY?

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Zellerbach Family Professor of Psychology, University of Pennsylvania; best-selling author
We Are Alone

If my math had been better, I would have become an astronomer rather than a psychologist. I was after the very greatest questions and finding life elsewhere in the universe seemed the greatest of them all. Understanding thinking, emotion, and mental health was second best — science for weaker minds like mine.Carl Sagan and I were close colleagues in the late 1960's when we both taught at Cornell. I devoured his thrilling book with I.I. Shklovskii (Intelligent Life in the Universe, 1966) in one twenty-four hour sitting, and I came away convinced that intelligent life was commonplace across our galaxy.

The book, as most readers know, estimates a handful of parameters necessary to intelligent life, such as the probability that an advanced technical civilization will in short order destroy itself and the number of "sol-like" stars in the galaxy. Their conclusion is that there are between 10,000 and two million advanced technical civilizations hereabouts. Some of my happiest memories are of discussing all this with Carl, our colleagues, and our students into the wee hours of many a chill Ithaca night.And this made the universe a less chilly place as well. What consolation! That homo sapiens might really partake of something larger, that there really might be numerous civilizations out there populated by more intelligent beings than we are, wiser because they had outlived the dangers of premature self-destruction. What's more we might contact them and learn from them.

A fledging program of listening for intelligent radio signals from out there was starting up. Homo sapiens was just taking its first balky steps off the planet; we exuberantly watched the moon landing together at the faculty club. We worked on the question of how we would respond if humans actually heard an intelligent signal. What would our first "words" be? We worked on what would be inscribed on the almost immortal Voyager plaque that would leave our solar system just about now — allowing the sentient beings who cadged it epochs hence to surmise who we were, where we were, when we were, and what we were (Should the man and woman be holding hands? No, they might think we were one conjoined organism.) SETI (the Search for Extraterrestrial Intelligence) and its forerunners are almost forty years old. They scan the heavens for intelligent radio signals, with three million participants using their home computers to analyze the input. The result has been zilch. There are plenty of excuses for zilch, however, and lots of reason to hope: only a small fraction of the sky has been scanned and larger more efficient arrays are coming on line. Maybe really advanced civilizations don't use communication techniques that produce waves we can pick up.

Maybe intelligent life is so unimaginably different from us that we are looking in all the wrong "places." Maybe really intelligent life forms hide their presence.So I changed my mind. I now take the null hypothesis very seriously: that Sagan and Shklovskii were wrong: that the number of advanced technical civilizations in our galaxy is exactly one, that the number of advanced technical civilizations in the universe is exactly one.What is the implication of the possibility, mounting a bit every day, that we are alone in the universe? It reverses the millennial progression from a geocentric to a heliocentric to a Milky Way centered universe, back to, of all things, a geocentric universe. We are the solitary point of light in a darkness without end. It means that we are precious, infinitely so. It means that nuclear or environmental cataclysm is an infinitely worse fate than we thought.

It means that we have a job to do, a mission that will last all our ages to come: to seed and then to shepherd intelligent life beyond this pale blue dot.