Jane Jordan and I tried not to get too excited. A signal picked up while observing target 4505, a star very slightly dimmer than the Sun thats 117 light-years away, was persistent and passing all the usual tests. We moved the telescope off the star system, and the signal went away. We ran it back on the target, and the signal reappeared. It was looking good. We continued to examine 4505 until the Earths rotation took it beyond Arecibos field of view, and it looked good all the while.

One of these days, this small scenario may end differently. And occasionally we think about that.

The Project Phoenix control room is no more than a small alcove off the main Arecibo observing complex: a long table, three workstations, and a few chairs. Thanks to our SETIcams and modern communications in general, this tiny hunk of real estate is open to the world, a fishbowl made of electronic glass.

But sometimes, late at night when the sounds of the frogs mix with the deep groan of the telescope motors, you can feel very isolated. It strikes you how odd it all is. Here we are, sitting in a cramped room somewhere in the rural, limestone hills of western Puerto Rico as much a random location on the globe as any and were trying to find the delicate traces of what are surely mammoth, enormously accomplished civilizations on worlds hundreds of trillions of miles above our heads. Distracted as we are by the day-to-day problems of keeping the equipment going and the routine obligations of observing, its easy to forget this and even to lapse into the unconscious assumption that tomorrow will always be like today: to accept that each night we will climb into our bunks still not having found a signal from space.

An experience such as we had for star 4505 disturbs this peaceful outlook. What would happen if we did find a signal? Its hard to think about that. The idea of changing the course of human affairs, as a SETI detection surely would, is so daunting that the reasonable mind protects itself by putting thoughts of it on hold. But if we cant envision success, why bother to try? I cant believe any SETI researcher would spend weeks tending a telescope on the assumption that a detection will never come. Its just that success would be a surprise: inevitably, a surprise.

In other words, when the signal comes in, no one is going to be leaping from his or her chairs. Theyre not going to be pumping adrenaline or shouting into phones. No, when the signal comes in, its going to look like more interference just another man-made squeal to be stuffed into the database so that we dont trip over it again. It will occasion neither comment nor commotion. All that will come later, when the signal is confirmed as something more than interference along with the excitement, the confusion and whatever response the world musters.

Its after midnight. Jill Tarter has taken over the observing, so I walk outside the control room to the patio that overlooks the telescope. Overhead, the familiar winter constellations prick the humid air. Is there more out there than simply the frigid blackness of space and the silent boiling of the stars? Are there hidden places where the sounds of life are being made and heard? Do beings exist that can see the universe and understand what they see? It seems impossible to imagine otherwise.