A small fraction of a tiny existence in an ancient universe: that’s how long we’ve actively listened for a very special signal. One type of signal out of perhaps infinite possible signals in a seemingly endless sky: those are the odds that are stacked against us. Is it worth it?

The search for other intelligent life in the universe is not an easy one. However, Seth Shostak, the senior astronomer for the SETI (Search for Extraterrestrial Intelligence) Institute, firmly believes that it is not only worth it, but that E.T. is just around the corner. In an upcoming issue of Acta Astronautica, a space science journal, Shostak predicts that we will receive a signal from other intelligent life sometime in the next 20 years. While other scientists have attacked the basis of his prediction, there are many who share his optimism. The combination of many new technologies and projects in both radio astronomy and the search for Earth-like planets lend new hope to the seemingly impossible search for other intelligent life.

Shostak’s prediction comes at a time when SETI is on the verge of what could be several of the most important advances in its history. The SETI Institute, a privately funded organization, and the University of California at Berkeley are building the Allen Telescope Array, the equivalent of a 100-meter radio telescope that will be simultaneously used by radio astronomers and SETI researchers 24 hours a day. This will be the first telescope of its kind devoted to SETI observing, enabling SETI researchers to focus in detail on hundreds of thousands of stars, if not millions.

Approaching the search for extraterrestrial intelligence from a different angle is the SETI League, a grassroots, nonprofit organization. The SETI League traditionally lets its independent members decide how they want to contribute. They mostly use smaller, amateur radio telescopes and may decide which frequencies to scan for. This allows for much more overall coverage of the sky with less sensitivity than the SETI Institute’s studies.

The Arecibo Observatory: largest radio telescope in the world. (Courtesy of the National Astronomy and Ionosphere Center, Cornell University, and the National Science Foundation)

“The SETI League concentrates on those frequencies which can best be processed on small backyard dishes,” says Paul Shuch, executive director of the SETI League. “We do not dictate to our members what those frequencies must be.” The SETI League’s new contribution to SETI is Project Argus, a coordinated attempt between 5,000 radio telescopes to observe the entire sky at the same time. Members of the SETI League hope to observe electromagnetic radiation from intelligent life that could be several hundred light years away.

Another boost for SETI comes from a relatively new kid on the astronomy block: planet-hunting. With an ever-increasing number of planet findings and advances in the tools and methods in finding planets, both astronomers who search for planets and SETI researchers hoping to refine their search have much to be hopeful for. Nine planet discoveries in the year 2000 prompted more attention to this growing field. Now, NASA is planning to launch the Kepler Mission, a targeted search for Earth-like planets.

An artist’s concept of an extrasolar planet. (Courtesy of NASA)

Perhaps no one is more optimistic about the search for extra-terrestrial intelligence than Bill Cochran, an astronomer at the University of Texas at Austin and one of the Kepler mission collaborators. A successful planet-hunter, Cochran, along with every other planet-hunter, has yet to find any Earth-like planets. However, Cochran expects the Kepler mission, a detailed, targeted, continuous study of about 170,000 stars over the course of 4 years, to turn up several Earth-like planets. As an experienced astronomer, though, he concedes with a shrug, “I don’t know what to expect. I’m always surprised by what happens.”

Planet-hunting and radio telescopes aside, is the prediction that we’ll find intelligent life in the next 20 years merited? Shostak based his prediction on more than just a new radio telescope. Using the well-observed Moore’s Law (that states the number of transistors fitting on a chip will double every 18 months as technology advances), Shostak calculated the future speeds at which SETI researchers will be able to sift through data.

“The speed of SETI has doubled every 18 months on average,” says Shostak. Even factoring in a more conservative estimate as chips get very small, SETI’s speed will still increase by orders of magnitude over the next 20 years.

An artist’s concept of the Kepler mission. (Courtesy of NASA)

Looking at Shostak’s prediction, there is still a missing piece. How do you know there is anything out there to search for? Scientists such as Paul Shuch have criticized Shostak for this part of his prediction.

“It would be nice to think that we know something about the existence, distribution, technology and motivation of our potential communications partners in space, but in fact, we don’t,” says Shuch.

Shostak used the Drake equation, a well accepted method in the scientific community for estimating the number of possible radio transmitters in the galaxy by the number of suitable stars and the estimated fraction of those with Earth-like worlds. Using an estimate of 10,000-1 million radio transmitters, he predicted that at least one would be detected in the next 20 years. However, Shostak concedes with a hint of optimism, “It could be that they’re wrong.”

There is still one other important problem related to the number of radio transmitters. What if E.T. doesn’t like electromagnetic radiation? Radio astronomers look for signals mostly in the microwave band of the electromagnetic spectrum. However, many astronomers and other scientists, including Cochran and Shuch, believe that other intelligent species would almost certainly use different forms of communication.

“Electromagnetic communication, appealing as it is to us, may be the exception rather than the rule,” says Shuch.

Cochran has his own opinions about searching for radio waves, a method of communication he believes would be very inefficient for an advanced civilization. Peering out of his 9th story office and scanning the Austin skyline, he explains, “It would be like us looking for smoke signals as a sign of life.”

Where do all these pieces leave the search for extraterrestrial intelligence? If nothing else, advances in astronomy and technology will change and improve SETI over the next 20 years. Telescopes are faster and more sensitive and search techniques are constantly improving. Soon, planet-hunters will narrow down the search even further. The odds may still be stacked against SETI, but they are getting better. Shuch believes that E.T. delivers no guarantees for contact in the next 20 years, but that doesn’t mean the search should stop. When asked about recent advances and the future of SETI, Shuch comments, “Even if we never hear a whisper from the stars, those advances will benefit humanity.”

The SETI Institute: www.seti.org

Planet Quest: http://planetquest.jpl.nasa.gov/

The Kepler Mission: http://www.kepler.arc.nasa.gov/