Second, we must analyze the signal to be certain that it is not coming from a human source.

Third, if the signal is detected repetitively, we can analyze it under the assumption that it might have content E.T. wants to share with us. Whatever that message might be—the digits of Pi, the first prime number, their encyclopedia, or some images of themselves—we can quickly find out if ET is trying to tell us something, and what that something is.

We are not there yet. In the past, especially during the tumultuous history of SETI, astronomers briefly thought that they had discovered a signal (see “Aliens on Line 1”). As technology evolves, and more searches occur, we may discover more signals that look promising at first but don’t pan out. But the search continues… in fact, in the scale of the age of our solar system, it has just begun.