Life an entity capable of reproduction, and of acquiring, organizing, and using material and energy for its own ends exists elsewhere in the universe. No scientifically trained person doubts this, unless mythologies cloud his mind. The odds in favor are just too overwhelming. [See subsequent note on this.] But what of "intelligent" life? There's less consensus here. And what of our current effort to locate such, if it exists?
SETI is searching for intellect in space. No one knows what to do if they find it.
"SETI" is a program of the nonprofit SETI Institute, that uses available time on major radio telescopes around the world to scan the sky for electromagnetic radiation of a sort that might emanate from intelligent beings elsewhere in the universe.
SETI (and the entire practice of astronomy) always receives signals from the past, and thus it searches for evidence of past intelligent life. Whether the generators of any signals we might detect are still around is a question we may not be able to answer. Now, how far in the past? is an interesting question.
Although it would be possible to receive signals from outside our own galaxy (the Milky Way) such signals would take at least two and a half million years to reach us, because of the distance to the nearest galaxy, so it's understandable that there is greatest interest in possible signals from within the Milky Way. There's plenty to pick from here. The Milky Way contains perhaps as many as 400 billion stars, the farthest of which are some 70,000 light years away. There are about fifty stars within 16 light years of our solar system, but no habitable planet has been detected among these stars, nor has any artificial signal been detected.
If SETI eventually discovers something that looks like an intelligent message, the first reaction both among scientists and in the press will be to cheer. We will (perhaps) have made a major but not surprising discovery: Other intelligent beings exist (perhaps). The next question will be, what to do with this finding. This is where the SETI objectives seem to get fuzzy. If we find signs of intelligence we'll feel good about it and we'll find it interesting. But the signal will more likely than not have come from many thousand light years away. That is, it was sent from its source many thousands of years ago. We could try to respond to the signal, but our reply would take equally many thousands of years to get back to the source, and then we won't know if "they" received our message for yet many thousands of years while their reply returns to us. Hardly conducive to meaningful communication.
The other, often overlooked, problem with communicating with extraterrestrial intelligence stems from the fact that they would certainly be a far more advanced form of life. Why? Because our civilization is in its first hundred years of being able to send signals that could be picked up in outer space. Any life forms sending signals across space that we might pick up would probably have sent them thousands of years ago, and would today be that many thousand years advanced. Even more telling is the thought that if we postulate that an intelligent civilization might survive from the time it learned to transmit radio waves say, ten million years, what is the chance that any signal we might intercept comes from a civilization in its first century of "radio civilization" like ours? It would be 10,000,000:100, or a hundred thousand to one. The chance would be 99 out of 100 that the transmitting civilization would be more than one hundred thousand years farther advanced than us, and it would be 90 percent certain that it would be more than a million years farther advanced. These are just examples though reasonable ones but it's a virtual certainty that the strangers would represent a very far advanced form.
Anyone who thinks that a meeting of humans with such advanced creatures would be a pleasant experience should think again. Our species would be treated by such beings as a curious find, perhaps the way humans have treated monkeys and apes. If we avoid serving as food for the visitors, or being wiped out as a nuisance, we could at best hope to serve science by being experimented upon. Or we might simply serve as slaves. The naοvete of those who actually wish to try to communicate with advanced extra-terrestrial intelligence is astounding. We'll be thankful for the fact that as long as the Relativity Theory holds, such communication appears to be stymied by time and distance.