E.T. hasn't phoned yet, but perhaps he's left a light on in the window.
Figuring an advanced civilization would hand out its galactic calling cards on powerful laser beams instead of microwave signals, astronomers in the United States are building the country's first telescope dedicated to looking for E.T.'s optical beacon.
The 72-inch scope, under construction at the Harvard-Smithsonian Oak Ridge Observatory in Harvard, Mass., is one of several new efforts that hope to answer the age-old question: Are we alone in the universe?
"We've got organic molecules in space, we've got planetary systems, we have life right away on Earth," and microbial life in extreme environments on our planet, says Harvard University astrophysicist Paul Horowitz, who heads the new telescope project. "What do you need to convince yourself that this is a normal phenomenon?"
While no one is trying to communicate with molecules or microbes, the galaxy has been around long enough for life to have emerged and evolved to technological levels exceeding our own - at least in principle.
For years, scientists searching for extraterrestrial intelligence (SETI) have used radio telescopes to search for signals from alien civilizations.
So far, they've come up dry. While those efforts will continue, Dr. Horowitz says, many in the SETI community have come to appreciate the promise light may hold for making first contact.
"Optical wavelengths have a lot of advantages that would make lasers the method of choice," Horowitz says.
A laser beam, for example, can pack more information than radio. Although galactic dust would block long-haul communications, he adds, visible light "works well for regional and local calling" - out to about 1,000 light years.
Easy to build for E.T.
If technological neophytes such as humans can figure out how to build them, laser transmitters would be a snap for more advanced cultures.
Horowitz figures that if scientists used the 10-meter Keck scopes in Hawaii to send billionth-of-a-second laser pulses, the beam blasting from the scope would shine 1,000 times brighter than our sun.
Those pulses would be easy pickings for another 10-meter telescope 1,000 light years away. Within that distance, astronomers estimate the sky holds roughly a million sun-like stars.
The concept of optical communications between solar systems is hardly new. In 1961, three years after Arthur Shawlow and Charles Townes announced their invention of the laser, the duo published a paper in the journal Nature describing how lasers could be used for SETI work. But the concept failed to catch fire in the US as a means of searching for other civilizations.
The reasons have less to do with technology than with technological prejudices in the SETI community in the 1960s and '70s, according to Stuart Kingsley, an electronics engineer who has long championed optical SETI efforts.
From radios to lasers
He notes that during those two decades, the Russians were using telescopes to look for optical signals from beyond our solar system. But in the US, SETI efforts focused on using large radio telescopes.
In the past four years, however, a growing number of researchers at institutions such as Harvard, Columbia, and the University of California at Berkeley, have been developing optical approaches to SETI projects.
Nor are such projects limited to PhDs. Dr. Kingsley has spent nearly 11 years developing a backyard optical SETI observatory, using a 10-inch amateur telescope.
He and Monte Ross, who heads a laser-communications company in St. Louis, hope to pull together a relatively inexpensive package of detectors and software that would allow amateur astronomers to take part in a coordinated, Internet-linked optical-SETI project.
As with radio searches, optical-SETI projects remain privately funded. Congress banned the use of federal funds for SETI work in 1993.
The Planetary Society, for example, is paying $350,000 to finance Horowitz's project. It plans to announce its sponsorship today in San Jose, Calif., where optical-SETI aficionados are holding their third annual conference.
Other projects under way
The Harvard project is just one outcome of meetings held in the late 1990s by the SETI Institute, a nonprofit organization in Mountain View, Calif., to chart the future course of SETI efforts.
Another key project under way is the construction of a $26 million 1,000-dish array of radio telescopes at Berkeley's Hat Cree Observatory in northern California.
The observatory, whose individual dishes aren't much larger than backyard satellite-TV dishes, is designed to allow SETI researchers to conduct their own searches while radio astronomers use the facility for more mainstream studies.
In addition, Berkeley's two-year-old SETI@home project is moving into a new phase that will use personal computers, in homes and offices around the world, to sift through radio-telescope data from the Southern Hemisphere for E.T.'s signals.
Until now, the program has drawn its data from the Arecibo Radio Telescope in Puerto Rico. The project, which tied home PCs into the world's largest supercomputer, has logged more than 500,000 years of cumulative computing time since it began in the spring of 1999. More than 2.7 million people are taking part.
For all the effort, it's no surprise that searchers have found nothing so far, says Louis Friedman, executive director of the Planetary Society in Pasadena, Calif. Humans have been looking for only about 40 years. Over the longterm, he says, he gives search efforts a 50-50 chance of success.
The payback, however, would be enormous. "The discovery that we're not alone, that there are other beings close enough to us to have communications technology? There would be few moments like it in human history," he says.
(c) Copyright 2001. The Christian Science Publishing Society