Jill Tarter

Pioneer 10 did not show up last night, nor tonight when I looked. If indeed the spacecraft is pointing to the wrong part of Earth’s orbit, we won’t be here when the Earth moves back into a favorable alignment. If a spacecraft broadcasts and nobody listens, does it really broadcast? It is quite likely that P10 is no longer transmitting, no one expected it would last this long. Maybe nobody else out there is transmitting either.

Common question: What if everyone is listening and nobody’s transmitting? Shouldn’t we be doing what we want the extraterrestrials to do? Actually, no. Listening is the more reasonable strategy for an emerging technology such as ours. Indeed, because of our brash technological youth, we are loudly announcing our own presence right now through leakage radiation. We generate signals for our own purposes, which escape to space—primarily commercial radio and TV broadcasting. As the electromagnetic spectrum gets more crowded with transmitters, and energy costs push us toward greater efficiencies, our current broadcast transmissions will find their way onto optical fiber, or become increasingly noiselike in their structure. The narrowband signals that mark today’s transmissions as obviously artificial will be supplanted by broadband modulation schemes that will be harder to distinguish from astrophysical emissions. It has been suggested that this transition would be an obvious time to begin deliberate transmissions of beacon signals. Since that transition will probably happen within a decade or so, I think our culture will still be too young to take on the job of transmitting. Transmitting is costly, it is a long-term strategy, and it requires global consensus of humanity. We’re not ready. Who would speak for Earth? What would they say? Where would we find the commitment to keep on saying it? Another technological civilization isn’t likely to be looking toward Earth during the time that any short-lived message washes over them. It makes no sense to transmit until we can take the long view of ourselves and of our global civilization. The Long Now Foundation is working on a 10,000-year plan involving a clock and a library. That’s the sort of timescale that makes sense for transmitting.

Why do I claim that any technological civilization we detect will be much older than us? First, they could hardly be any younger. If they were they wouldn’t have the technology needed to be detected over interstellar distances. We are a very young technology in a very old galaxy. Second, if we succeed in finding them anytime soon with our primitive equipment (that we are all duly proud of), then they have to be relatively close by. This will only happen when technological civilizations survive for a long time. Many stars in the Milky Way are twice as old as our sun. Our neighbors could be millions or billions of years older than we are (they just couldn’t be younger and be detectable). They might have no desire to contact us. Or there may be some galactic club alliance that keeps an eye out for emerging technologies, such as we are, and a desire to keep the transmitters going.

What will I do if we detect a signal? First, I’ll follow the procedures we’ve written out (so we get it right) to check out the detection. If possible I’ll arrange for an independent confirmation because we worry about hoaxes. If it still looks good, I’ll make a courtesy call to our major donors and then send an IAU Telegram (actually an e-mail, but the name is historical) to astronomical observing facilities worldwide, so they can use their instruments to continue studying the source of the signal. A press conference is a necessity, to tell the world. I’ll drink champagne to celebrate with my team, and then maybe I’ll get some sleep and let somebody else do the observing. I will have my answer.