But the time scale, even for Horowitz, is unclear.

“We’ve had this technology for about a century. That’s about zero on the time scale of geologic history,” Horowitz observes.

For now, Horowitz’s graduate student, Mead, is taking up the intergalactic mantle. Mead is now working on improving SETI’s All-Sky Optical Telescope to be 100 times more powerful and extend detection into the infrared.

NAYSAYERS

Not everyone holds such confidence in finding intelligent life on distant planets.

Benjamin M. Zuckerman of the UCLA Astronomy Department represents one of the strongest academic voices in the camp of extraterrestrial naysayers.

Zuckerman, who completed his doctoral thesis in astronomy at Harvard in 1968, recognizes in his book “Extraterrestrials: Where Are They?” that there is no evidence intelligent life exists. And if it did, he says, why haven’t they contacted us yet?

Zuckerman’s path toward skepticism was borne out of unfulfilled aspirations. At Harvard, Zuckerman worked down the hall from Astronomy Department Assistant Professor Carl Sagan, famous for bridging science into popular culture through works such as the Hollywood film “Contact” and his hit TV show “Cosmos.”

The two scientists frequently discussed the prospects of finding extraterrestrial life, and Sagan’s dream of proving that man is not alone among the stars eventually rubbed off on Zuckerman. In the 1970s, Zuckerman canvassed the cosmos for intelligent life using radio telescopes in the hopes that a signal from otherworldly technology could be detected. Today, after years of fruitless searching, Zuckerman says he no longer believes that there are other planets with detectable intelligent life, at least in the Milky Way Galaxy.

He considers himself “agnostic” as to whether planets have lower life forms, such as microbial organisms and what may be comparable to animals and plants on Earth. The existence of these types of life forms, he says, is more difficult to refute because the argument that they would have intentionally contacted earth is irrelevant.

RISE OF THE EXOPLANET

Astronomy professor David Charbonneau, who received his Ph.D. in astronomy from Harvard in 2001, is one of the world’s leading experts on exoplanets, planets that orbits stars outside our own solar system. He is also the director of undergraduate studies for the Harvard Astronomy department and a researcher at the Harvard-Smithsonian Center for Astrophysics.

And Charbonneau says that within three years, man will likely discover habitable planets on which life could thrive.

“What I will tell [my students] in the first lecture is, ‘If you’re a freshman, you will probably be an undergraduate at Harvard when you hear about the discovery of the first habitable exoplanets.’ It’s really going to happen.”

Charbonneau says his research into exoplanets is driven primarily by the question: “Can we find an analogue of the Earth?”