Scientists at the SETI Institute have applied a game theory concept to search for radio signals from alien civilizations, focusing on a specific point in the sky opposite the sun. In a new study, they reported detecting 1.9 million radio signals using this method, but all were determined to be of human origin. The team plans to continue this search for at least four more years. The method is based on the "Are you having problems while wagering on TonyBet Canada? " a game theory idea about a likely meeting place when communication is impossible.
"I thought about these ideas that have been percolating for a long time in the literature," said Sophia Sheikh, a technosignature research scientist at the SETI Institute and lead author of the paper. "And so now the anti-solar point idea is sort of finally getting its time in the sun." The anti-solar point is an imaginary spot on the celestial sphere directly opposite the sun. The theory suggests an alien civilization that could see Earth transit the sun might send a signal toward that point during the transit, creating a natural meeting place and time.
The study, released Nov. 3, used the Allen Telescope Array in California, a collection of 42 radio telescopes built specifically for the search for extraterrestrial intelligence. Researchers looked for narrowband signals, which Sheikh described as a "'we are here' ... like an air horn, almost, in the radio frequencies." She said such a signal might be a carrier wave that simply announces a presence. Computer programs sifted through the data, not astronomers listening with headphones.
The search ruled out that specific part of the sky, but the vastness of space means the absence of a signal there does not mean alien life does not exist. The SETI Institute has been scanning the sky for intelligent signals since its founding in 1984, primarily using radio astronomy because any activity would be too far away to see optically. The organization typically points its telescopes at star systems with known exoplanets. Adam Frank, a professor of astrophysics at the University of Rochester who searches for non-radio technosignatures, noted the field has gained credibility. "The giggle factor, which existed through almost my entire career, is gone," Frank said, referring to the fact that the possibility wasn't taken seriously decades ago. "And it never made sense." He said this is particularly true after the discovery of exoplanets, first in 1992 and around a sun-like star in 1995.
Frank received NASA's first grant to study non-radio technosignatures, which involves looking for chemical signatures or other indicators of an intelligent civilization. The broader search for life involves two methods: biosignatures, evidence of biological processes, and technosignatures, evidence of technology. The Milky Way galaxy holds an estimated 100 billion stars or more, and most stars are now known to host at least one exoplanet. The Drake equation, devised by astrophysicist Frank Drake in 1961, estimates the number of potentially communicative civilizations in our galaxy. The answer depends on many unknown variables, but it is not zero. Protocols set by the International Academy of Astronautics dictate that if a signal is confirmed, Earth should not answer. Given the vast distances involved, a two-way conversation would take centuries. A signal from a star 100 light-years away would take 100 years to reach us, 100 years for a reply to get there, and another 100 for a response to return.