50 Years of Alien Hunting Yields No Result - A New Era of SETI Program is About to Begin
On May 6, according to foreign media reports, it has been nearly 50 years since scientists first proposed searching for alien radio signals. Although strange signals occasionally appear, we have not yet clearly heard the cosmic calls from aliens. Now experts in the Search for Extraterrestrial Intelligence (SETI) program are beginning to question: could we have been looking in the wrong place for the wrong signals?
Perhaps our search hasn't gone far enough?
Senior astronomer at the SETI Institute, Seth Shostak, explores all these possibilities in his new book "Confessions of an Alien Hunter." Shostak's "confession" is actually his argument for the meaningful reasons behind the search for extraterrestrial intelligence. Whether it is necessary to search for aliens has always been a controversial topic among people, with some dramatic events occurring along the way, such as the most famous forgery in alien hunting (including articles Shostak wrote for MSNBC.com ten years ago) and some metaphors that might embarrass Dan Rather (including "Life Is as Durable as Fruitcake").
The SETI Institute where Shostak works is a major proponent in the search for alien signals. The quest for extraterrestrial life can be traced back to 1960 when astronomer Frank Drake (now the chairman of the SETI Institute) pointed an 85-foot diameter infinite telescope at the sky in West Virginia, hoping to make contact with aliens. Afterwards, Drake and his colleagues continued using larger and better-performing telescopes, including the 400-foot diameter Green Bank Radio Telescope and the 1000-foot diameter Arecibo Observatory. However, the strategy was basically the same: checking for unnatural stable radio signals from one star, then turning to another.
Now, everything has changed. The Allen Telescope Array, jointly established by the SETI Institute and the University of California, Berkeley, can simultaneously study multiple stars. Like microchips, the efficiency of SETI is improving geometrically according to Moore's Law. Shostak pointed out that at this rate, within 24 years, it will be possible to check the signals from over a million stars.
Will we finally make contact?
Shostak and Drake believe that sampling will be crucial for ultimately making contact. First, assuming aliens exist, they would likely think about things the way we do. The first assumption is important, but the second is even more so. If finding traces of microbial life on Mars and beyond requires us to accurately understand astrobiology, then searching for life outside our solar system may require understanding more, perhaps even astro-psychology?
For decades, the strategy of SETI has been dominated by the "Cosmic Golden Rule" — seeking communication with aliens through channels we ourselves use. A generation ago, it might have been analog TV signals, sending "I Love Lucy" into space. Today, Drake estimates that aliens might use digital transmission, employing lasers rather than radio antennas. Over a weekend in Seattle discussing this matter, Drake pointed out that the newly built National Ignition Facility in the United States can focus 192 laser beams into a pulse lasting a few billionths of a second, brighter than the sun. He said, "These lasers can create light pulses visible to all mini-telescopes in the galaxy."
Shostak's theory is that aliens might have two types of signal emitters: one that flashes, like light pulses aimed at a series of potentially habitable target planets (including Earth), and another that broadcasts low-energy omnidirectional radio signals, telling you how to join their book club or something else. For this reason, alien hunters have begun surveys to detect these faint lights and continuous radio communications.
So where should we look?
All along, the SETI Institute's list of targets has favored Earth-like planets we believe could harbor life. However, in "Confessions of an Alien Hunter," Shostak suggests that based on our understanding of artificial intelligence, the most likely aliens sending signals might actually be AI machines. In an interview, Shostak admitted that if aliens are large robots, then the strategy of targeting Earth-like planets orbiting Sun-like stars might end up being "a very outdated idea." He said, "A place where everything can rust might not be the best place for aliens." From the perspective of such machines, a better location would be in the orbit of a star hot enough to provide the massive energy needed to transmit signals.
However, Drake argues that we should not overlook the other end of the stellar spectrum. About three-quarters of the stars in our galaxy are red dwarfs, which are dimmer than the Sun but still could potentially provide homes for aliens. These stars have been overlooked in previous searches for extraterrestrial civilizations. When mentioning the observation of such potentially life-harboring stars in the universe, Drake noted that our simple photographs are too simplistic. One of the reasons Drake remains undeterred despite the lack of results after 50 years of SETI is that only about 1,000 stars have been studied, which is just a few percent of the possible stars to investigate.
Shostak stated that he is confident in finding reliable evidence of extraterrestrial life within the next 24 years, possibly through the SETI program, atmospheric analysis of exoplanets, or digging soil on Mars and ice on Europa or Enceladus. Drake believes that finding this evidence might take longer, saying, "I don't think we'll find it by 2025 unless we're extremely lucky. It might take twice as long, perhaps until 2050." Other scientists estimate this timeframe to be 100 to 200 years. Of course, global assumptions about the timeline for SETI will continue to attract followers and discoveries. The U.S. SETI program is privately funded rather than government-funded, and Drake noted that fundraising has become more difficult now. He said, "As long as the economy continues to slump, we must adjust this timeline."
Will these experts eventually announce that there are no aliens? What will Shostak do if there's still no result after a century of searching? He said, "If there really are no aliens, I don't know what I'd say, but I might say we got it wrong... We made a fundamental mistake."