When Should We Listen for Alien Signals? Scientists Turn to Game Theory

Scientists at the SETI Institute are using game theory to determine when and where to listen for extraterrestrial signals. They are conducting a multiyear search focused on the anti-solar point, a location in the sky that could serve as a common reference for two civilizations to coordinate communication. The study uses the Allen Telescope Array (ATA) at the Hat Creek Radio Observatory in Northern California. The pilot study did not find any evidence of extraterrestrial technology, but it marked an important milestone as the first observational search of the anti-solar point.

The research team suggests that the layout of the solar system could provide a common reference point for two civilizations to identify the same time and place to establish contact. The anti-solar point is the direction opposite the Sun from Earth's perspective during a solar transit. The study uses the ATA’s beamforming capability to compare signals from the ASP to a different point in the sky, helping filter out human interference. The first observations collected 17 hours of data, generating 32 terabytes of data and found about 1.9 million radio signal detections, but none that matched extraterrestrial technology.

The survey is planned to run two to three nights each week, aiming to cover all the important positions along Earth’s orbit over about four years. The researchers have created an automated process to handle the huge amount of data from their observations. The pilot study established the first observational limits for radio transmitters using the anti-solar point as a possible communication strategy. Under certain assumptions, the observations were sensitive enough to detect signals from a transmitter comparable in power to the former Arecibo planetary radar at distances of up to approximately 124 light-years. The survey has already gathered more than 121 nights of observations since the pilot study. Results from the first year of data will be shared in a future publication.

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