The search for extraterrestrial intelligence is, some would say, too passive — it’s pure listening, monitoring radio and, in some cases, optical wavelengths in hopes of intercepting either a message from another civilization or, perhaps, catching a snippet of its internal communications. But is there a place for an active SETI, one that is just as anxious to send a human message to the stars as to listen for the broadcasts of others?

Not that there haven’t been previous attempts to send signals, the most famous of which was the 1974 Arecibo message beamed in the direction of M13, a globular cluster in the constellation Hercules. The Hercules message, containing binary representations of the human form, the solar system, and other mathematical and chemical information, pushes us into the domain of long-term thinking, for it will take 25,000 years to reach its target (and, obviously, another 25,000 years for any reply). But M13 is also an interesting place to send a signal, for it is one of the oldest objects in the heavens; the globular clusters date back to the early days of the universe.

Sure, Arecibo was a ‘proof of concept’ message more than anything else, but some big names have endorsed the active SETI approach, including Russian physicist Andrei Sakharov, who said this in 1971 (three years before the Arecibo message was sent): “I would like to notice the importance of designing and, especially, accomplishing practical projects directed to sending signals. This is the only way to understand the subtle problems of contact.”

Image: Messier 13, a globular cluster containing roughly one million stars in the halo of the Milky Way. It lies in the constellation Hercules, 25,000 light years from the Sun. What will life on Earth be like when the Arecibo signal reaches M13? Credit: Robert Lupton, The Sloan Digital Sky Survey.

Now a guest editorial for the SETI League, written by Dr. Alexander L. Zaitsev and colleagues, makes the case for continuing the active approach. Zaitsev is Chief Scientist of the Radio Engineering and Electronics Institute of the Russian Academy of Science. He uses the acronym METI: Messaging to Extraterrestrial Intelligence. And he has conducted three transmissions, all sent from the Evpatoria Planetary Radar facility in the Ukraine, and all containing, in addition to scientific information, a mixture of art, music, and video.

The chief argument against two-way communications at interstellar distances is that it simply takes too long, and here Zaitzev quotes Carl Sagan to great effect:

“For those who have done something they consider worthwhile, communication to the future is an almost irresistible temptation, and it has been attempted in virtually every human culture. In the best of cases, it is an optimistic and far-seeing act; it expresses great hope about the future; it time-binds the human community; it gives us a perspective on the significance of our own actions at this moment in the long historical journey of our species.”

Such long-term thinking is precisely what we need as we confront the great imperative of interstellar exploration. Our first interstellar probes may well take hundreds of years to reach their destination. When I talked to NASA’s Les Johnson at Marshall Space Flight Center in Huntsville, I had mentioned Gregory Matloff’s interstellar ark concept, a huge sail-driven spacecraft that would take a millennium to reach Alpha Centauri.

“A thousand years?” Johnson said. “If we were to launch a voyage like that today – if we could design a spacecraft to last that long – which is a big if – you could see that it might still be a useful thing to do because chances are, barring some catastrophe, records of that launch would survive a thousand years. And people would know to listen on that arcane radio band, whatever it is, for what comes in from Centauri. Get that mission time down to a hundred years and yes, absolutely, that’s workable.”

As to SETI and METI, my thought is that while neither is likely to succeed, both are worth attempting because they teach us to think in terms that extend well beyond the average human lifetime. The world is enriched today by the monuments left behind by those who believed their work was a gift to the human future. If we can build the scientific base for generations yet unborn to make a communications or propulsion breakthrough that will take us to the stars, then the ground-breaking for that edifice should continue whether or not any of us will live to see the results.