This post originally appeared on Franck Marchis' Cosmic Diary blog and is reposted here with his permission.
Several readers have contacted me recently about reports that a group of international astronomers have detected a strong signal coming from a distant star that could be a sign of a high-technology civilization. Here’s my reaction: it’s interesting, but it’s definitely not the sign of an alien civilization—at least not yet.
But—and it’s a big but—I began this post by saying “at least not yet.” So what might cause me to change my mind? How might we prove the extraordinary claim that this signal is, in fact, a civilization trying to communicate with us?
We turn to this mantra from Carl Sagan: “Extraordinary claims require extraordinary evidence.” That means three things:
First, this signal must be detected by at least one other antenna located somewhere else in the world. My colleagues at the SETI Institute are already working on it, and have observed the star for several hours. So far they have nothing to report.
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.