For thousands of years, humans have wondered if the cosmos hosts other civilizations.
Now, the hunt for ET is set to shift into high gear with the announcement of a $100 million, 10-year search that involves two large radio telescopes to hunt for radio signals, plus an optical telescope to look for evidence of laser communications.
The scale of the effort, known as Breakthrough Listen, is unprecedented. Until now, the hunt for signals generated by intelligent life elsewhere in the universe has operated on a shoestring and, at least early on, was widely seen as quixotic.
But evidence on Earth that simple forms of life can thrive in environments hostile to humans, as well as the discovery of thousands of planets orbiting other stars, has added energy to the effort. The discovery of these extrasolar planets has led to estimates that the Milky Way alone holds billions of Earth-mass planets orbiting within their host star's habitable zone – a distance at which liquid water, essential for organic life, can persist on a planet's surface.
This time, the new project's funding levels, the list of scientists steering the effort, technological advances, and the effort's open-data policy ensure that participants will receive substantial amounts of precious observing time at the observatories involved. This puts the effort in the best position yet to make advances in the search for extraterrestrial intelligence (SETI).
"Our generation, or maybe the next one after that, has a reasonable chance of finding the answer to this question: Are we alone?" says Dan Werthimer, a researcher at the University of California at Berkeley and a member of the new project's steering group.
The answer is profound, whether it is yes or no, says Dr. Werthimer, who also plays a lead role in several other search efforts, including SETI@home and SERENDIP.
If the universe is teeming with intelligent life, humans could learn from older civilizations how they have survived for so long and apply those lessons on Earth, he explains.
And "if we do find that we are alone, or life is incredibly scarce, we'd better take really good care of life on this planet," he adds.
Over the past several decades, SETI efforts in the United States have survived on modest grants from organizations such as the National Aeronautics and Space Administration and the National Science Foundation, or from private funders such as the Templeton Foundation. Globally, spending on SETI projects currently runs about $2 million a year, Werthimer estimates.
"I'm proud of the stuff we've been doing," he says. But "this is huge."
Funding for Breakthrough Listen comes courtesy of the Breakthrough Prize Foundation, whose founder, Yuri Milner, has pledged the $100 million. Mr. Milner, along with renowned physicist Stephen Hawking, announced the project and funding Monday.
Milner reportedly has expressed an interest in extending the project if the first 10 years fails to turn up signals from other civilizations.
The hardware involved includes a radio telescope with a 64-meter (210-foot) dish antenna at Australia's CSIRO Parkes Observatory, and the Green Bank Telescope, sporting a 100-meter antenna at the National Radio Astronomy Observatory in Green Bank, W.Va. In addition, an optical telescope originally designed to conduct automated searchers for extrasolar planets at the Lick Observatory atop Mt. Hamilton in California will take up the hunt for laser signals at optical wavelengths.
Unlike the current SETI workhorse, the Arecibo radio telescope in Puerto Rico, the dish-shaped antennas at Parkes and Green Bank can be readily aimed at different regions of the sky. Arecibo's 300-meter dish is carved into a saddle between summits, so its gaze is fixed.
Arecibo will continue to feed data into SETI efforts. But with Green Bank in the Northern Hemisphere and Parkes in the Southern Hemisphere, the two will combine to provide virtually complete coverage of the sky. They also sport state-of-the-art receivers that cover more frequencies and will allow observers to look at several points in the sky simultaneously. Additional receiver upgrades are expected to take place as time passes.
Overall, access to these facilities will yield a search that covers 10 times more sky and is 50 times more sensitive than previous efforts. The Breakthrough Listen team notes that if someone dropped an aircraft carrier on a planet orbiting any of the 1,000 stars nearest the sun, the two observatories could pick up the transmissions from the ship's radar.
Green Bank is making roughly 20 percent of its annual observing time on the 100-meter telescope available during the 10-year period. Parkes has agreed to open up 25 percent of its observing time for five years.
Telescope time is a precious commodity, notes Karen O'Neil, Green Bank's site director. So the Breakthrough Listen team has been working with other astronomers to ensure that the data gathered during a session is easy to use and immediately available to researchers interested in something other than SETI.
"It's exciting that a group that's willing to pay for time on the telescope desires to follow that model of open access to the data," Dr. O'Neil says.
It's all a far cry from National Radio Silence Day in 1924 – a 36-hour period in which the federal government requested radio silence from civilians for five minutes each hour on the hour. The government sought the quiet time to allow a receiver perched in a dirigible some two miles above Earth to listen for any signals that might be coming from Mars.
Ninety-one years later, Earth has yet to hear anything from ET. With nothing to show for detection efforts so far, some in the astronomical community and elsewhere undoubtedly will be scratching their heads at the resources that Breakthrough Listen will have at its disposal.
"There's always been skepticism, and there always will be skepticism, about whether it's the right use of a telescope,” O'Neil says.
It's an extreme example of a high-risk, high-reward project. "Will we detect something? There's a high probability that we won't," she acknowledges. "But boy, if we detected something, it would be amazing."
Indeed, members of the science team, which includes longtime extrasolar-planet hunter Geoffrey Marcy, bring with them a great deal of respect, O'Neil says.
"If they were to announce, 'We've found something,' people would listen," she says.