For all those folks out there who are counting the days until we hear from some intelligent creature on another planet, researchers now say we're not going to be able to eavesdrop on the space alien equivalent of "I Love Lucy."
During the few decades that scientists have searched systematically for life elsewhere in the universe there has been some hope that electromagnetic "leakage" from communications systems on other planets -- such as television broadcasts -- might be detectable from Earth. If that's the case, then radio telescopes sweeping the sky might pick up those signals, giving us a window onto other worlds, and finally answering that increasingly overworked question, "Are we alone?"
Don't count on it, say researchers from three institutions. Any advanced civilization would likely encode and compress its communications to make its systems more efficient, just as your computer compresses files that you send over the Internet, the researchers argue in a report in the American Journal of Physics.
And that, they say, would make those signals indistinguishable from the thermal radiation of stars, and thus impossible to detect because it would seem like part of the universe's background noise.
Even if we did somehow capture such a signal, we wouldn't know it, says physicist Mark Newman of the University of Michigan in Ann Arbor.
"If you don't know how to decode it, then you can't make out what's going on," Newman says.
A computer can't show a picture that has been compressed by another computer unless it knows how to decompress it, and likewise we couldn't decode a television signal that had been compressed unless we already knew the code. And, Newman and his colleagues argue, any advanced civilization that has used wireless communications for even a few decades would surely have figured out that it makes sense to encode.
We're already doing it, and we're just barely in the communications age.
"This is something we already do in many of our transmissions," Newman says. "We encode (compress) them so they take up less space and we can send them faster and send more messages."
To be fair, the Search for Extraterrestrial Intelligence has never been wedded to the idea that we could somehow tune in to alien television broadcasts. Astronomer Frank Drake, who many consider the father of the current effort, told me years ago that any such signal would probably be far too weak to detect on Earth.
Thus the primary aim is to find signals that are intentionally sent in our direction by another life form, and thus designed to be easily detected by us. Newman has been informed of that by many irate readers of his report who maintain that the search is viable because no one is really listening for Lucy.
Yet much of the SETI literature does suggest that ordinary communications signals might be detectable.
And that's what compelled Newman and biologist Michael Lachmann of the Max Planck Institute in Leipzig, Germany, and computer scientist Christopher Moore of the University of New Mexico in Albuquerque to take a closer look.
The three built on the pioneering research of Claude Shannon, an electrical engineer with Bell Labs who published two seminal papers in the 1940s on information theory. Shannon demonstrated that it is possible to compress data and thus distribute far more information than would otherwise be possible. That work is the foundation for much of today's communication technology.
Compressed data, however, looks like just a jumble of junk unless it is decoded, and the researchers wondered if that would apply to radio signals as well.
"In our paper we proved that there's an equivalent result for radio messages," Newman says. "The most information-rich radio message looks like thermal radiation, which is the standard kind of radiation that we see in the sky. So that would make it difficult to tell the difference between an intentional transmission that was very efficient and just natural phenomena."
But what if someone out there really is trying to contact us? That message would not likely be encoded because they -- whoever "they" might be -- would want us to understand it.
"Then, of course, you could easily see it," Newman admits.
Which takes me back about a dozen years to a time when I sat on the porch of Frank Drake's California home and listened to this eloquent scientist talk about the passion in his life, somehow finding ET.
He said all those years ago that routine signals from another planet would spread out as they passed through space, weakening as their footprint grew ever larger. And just as a flashlight grows dimmer with distance, they would probably be far too weak to detect by the time they reached Earth.
But what if someone is beaming a very tightly focused, high-powered transmission directly at us? Surely we could find that pretty easily.
Drake's enthusiasm has always been infectious, but I wondered out loud how long that enthusiasm would last. With trillions of stars out there, how long would he be willing to search? When might he decide that perhaps he was on the wrong track, that perhaps ET is elusive, or isn't interested in our primitive society?
I don't have the notes from that meeting, and couldn't reach Drake for this column, but I remember what he said. Picking a number out of the air, he said if scientists hadn't found anything in about 10 years, perhaps they would have to rethink their program.
The SETI Institute in Mountain View, Calif., which Drake helped found, has now grown into a large organization of more than 100 scientists and staffers, due largely to the largess of a number of folks with very deep pockets.
It is more than 20 years old now.
And in all those years of searching, not a single signal has turned out to mean anything at all. If ET is trying to reach us, she must not be trying very hard.
Lee Dye's column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.