Is Anybody Out There?
Absence of evidence is not the same as evidence of absence.
Donald Rumsfeld (on weapons of mass destruction)
What if ET calls tomorrow?
On a cold and misty morning in April 1960, a young astronomer named Frank Drake quietly took control of the 26-metre dish at the US National Radio Astronomy Observatory in Green Bank, West Virginia. Few people understood that this moment was a turning point in science. Slowly and methodically Drake steered the giant instrument towards a sun-like star known as Tau Ceti, eleven light years away, tuned in to 1,420 MHz, and settled down to wait. His fervent hope was that alien beings on a planet orbiting Tau Ceti might just be sending radio signals our way, and that his powerful radio dish would detect them.
Drake stared at the pen and ink chart recording the antenna's reception, its fitful spasms accompanied by a hiss from the audio feed. After about half an hour he concluded there was nothing of significance coming from Tau Ceti - just the usual radio static and natural background from space. Taking a deep breath, he carefully reoriented the big dish towards a second star, Epsilon Eridani. Suddenly, a series of dramatic booms emanated from the loudspeaker and the pen recorder began frantically flying back and forth. Drake almost fell off his chair. The antenna had clearly picked up a strong artificial signal. The astronomer was so taken aback he remained rooted to the spot for a long while. Finally, getting his brain in gear, he moved the telescope slightly off target. The signal faded. But when he moved the antenna back, the signal had disappeared! Could this really have been a fleeting broadcast from ET? Drake quickly realized that picking up a signal from an alien civilization on the second attempt was too good to be true. The explanation must lie with a manmade source and, sure enough, the signal turned out to be produced by a secret military radar establishment.
With these humble beginnings - whimsically called Project Ozma after the mythical Land of Oz - Frank Drake pioneered the most ambitious, and potentially the most significant, research project in history. Known as SETI, for Search for Extraterrestrial Intelligence, it seeks to answer one of the biggest of the big questions of existence: are we alone in the universe? Most of the SETI programme builds on Drake's original concept of sweeping the skies with radio telescopes for any hint of a message from the stars. It is clearly a high-stakes endeavour. The consequences of success would be truly momentous, having a greater impact on humanity than the discoveries of Copernicus, Darwin and Einstein put together. But it is a needle-in-a-haystack search without any guarantee that a needle is even there. Apart from one or two intriguing incidents (of which, more later) all attempts have so far been greeted with an eerie silence. What does that tell us? That there are no aliens? Or that we have been looking for the wrong thing in the wrong place at the wrong time?
SETI astronomers say the silence is no surprise: they simply haven't looked hard enough for long enough. To date, the searches have scrutinized only a few thousand stars within 100 light years or so. Compare this to the scale of our galaxy as a whole - 400 billion stars spread over 100,000 light years of space. And there are billions of other galaxies. But the power of the search is expanding all the time, following its own version of Moore's Law for computers, doubling every year or two, driven by surging instrument efficiency and data-processing speed. Now the scope is set to improve dramatically, with the construction of 350 interlinked radio dishes at Hat Creek in Northern California. Named after the benefactor Paul Allen, the Allen Telescope Array will enable researchers to monitor a much larger fraction of the galaxy for alien signals (see Plate 1). The facility is operated by the University of California, Berkeley, and the SETI Institute, which is where Frank Drake now works. The Institute remains upbeat about the prospects for success, and keeps champagne permanently on ice in anticipation of a definitive detection event.
It's easy to picture the scene if the optimism is right, and something is found soon. An astronomer sits stoically at the controls of the instrument, his feet stuck up on a desk cluttered with papers. Absently, he thumbs though a mathematics textbook. So it has been for him, and dozens of others engaged in SETI, for decade after decade. But today is different. Suddenly the bored astronomer is startled out of his reverie by the shrill, distinctive sound of an alarm. The screech is generated by a computer algorithm designed to spot 'funny' radio signals and separate them from the clutter continually being received from outer space. At first, the astronomer assumes it's just another one of those false alarms, usually a manmade transmission that slips through the net designed to filter out obvious artificial signals coming from mobile phones, radar and satellites. Adhering to the time-honoured protocol, the astronomer keys in some simple instructions and moves the telescope slightly off the target star. The signal immediately dies. He moves the instrument back on target and the signal is still there. After carefully studying the radio wave form and determining that the source remains at a fixed location relative to the stars, the astronomer quickly places a telephone call to a companion observatory involved in the project and simultaneously e-mails the coordinates of the mystery signal.
Five thousand miles away, another astronomer is called out of bed to investigate. Drowsily she wanders to the control room and pours herself a coffee. Then, shaking the sleep from her head, she checks her e-mail and enters the given coordinates. Within a minute the second radio telescope has locked on to the target and immediately picks up the same signal, loud and clear. Her pulse begins to race. Is it conceivable that this time the alert is for real? After decades of unrewarded search, might she be the first person on Earth to confirm that an alien civilization really exists and is transmitting radio signals? She knows that many more checks will be needed before leaping to that conclusion, but the two astronomers, now in excited telephone conversation between different continents, systematically eliminate one mundane possibility after another until, with 90 per cent certainty, they infer that the signal is indeed artificial, non-human and originating far, far out in space. As the radio telescopes continue to track in synchrony and record every minute detail, the dazed pair behave as if in a dream, stunned, awed and euphoric, all at once. What next? Who to tell? What can be gleaned from the data already gathered? Will the world ever be the same again?
The story so far (which I admit involves some literary licence) does not demand any great leap of imagination. The basic scenario was well enough portrayed in the Hollywood movie Contact, in which Jodie Foster plays the role of the lucky, overawed astronomer. What is far less clear is the next step. What would follow from the successful detection of an alien radio signal? Most scientists agree that such a discovery would be disruptive and transformative in myriad ways. Even contemplating a signal received out of the blue raises many questions: how and by whom would it be evaluated? How would the public get to learn about it? Would there be social unrest, even panic? What would governments do? How would the world's leaders react? Would the news be regarded with fear or wonderment? And in the longer term, what would it mean for our society, our sense of identity, our science, technology and religions? On top of these imponderables is the vexed issue of whether we should respond to the signal, by sending our own message to t...