Scientists propose using game theory to search for radio signals from extraterrestrial civilisations. This field relies on mathematically predicting an opponent’s most likely decisions. It predicts the existence of Schelling points—directions from which a message is most likely to arrive.
Where to Look for Aliens
For decades, the SETI programme has been listening to stars for extraterrestrial signals. Recently, a paper presented at the 77th International Astronautical Congress offered a new perspective on this process and, potentially, a new approach to the search. The website phys.org describes its findings.
The search for signals from extraterrestrial civilisations faces several problems. The biggest is that receiving them from most stars in our Galaxy is practically impossible because of the limited sensitivity of radio telescopes. However, this problem is overshadowed by another: even among stars within observational reach, there are so many that no search programme can cover them all.
The traditional approach is to listen to stars whose characteristics most closely resemble those of the Sun. However, Project Phoenix, which ran from 2012 to 2015 and examined more than 1,000 Sun-like stars without finding anything, showed that this approach offers no guarantees.
In the new study, the researchers therefore argued that selecting the most Sun-like stars is a good starting point, but there are still too many of them. The sample needs to be narrowed down so that more time can be devoted to each individual star. But how can the most promising ones be identified? This is where game theory comes in.
Game Theory and Aliens
Game theory is a kind of probability theory turned inside out. It relies on analysing all possible outcomes of all plausible decisions in a given situation and calculating their average payoff. It predicts that even in such an enormous system with many unknown factors, there should be so-called “Schelling points”—options where the probability of obtaining something is higher than elsewhere.
The central idea of the new study is that these are the antisolar points. These are directions defined by lines passing through the Sun and Earth and extending away from the Sun. Why do scientists think signals should be expected from these particular directions? Because observers located in those directions can see transits—the passage of our planet across the Sun’s disc.
It is important to remember that these points are not fixed, since our planet orbits the Sun. Moreover, both Earth and the Sun have non-zero radii. This means that these “Schelling points” are not actually points, but an entire zone extending along the ecliptic.
This, in turn, means that a complete survey cannot take less than one year, during which our planet completes a full orbit. However, a pilot programme conducted with the Allen Telescope Array from 2024 to 2026 showed that even this was insufficient for reliable detection. More precisely, around 1.9 million signals were detected during that period, but all turned out to be terrestrial in origin. The stars themselves had still barely been listened to, meaning that even this type of search needs to continue for at least several years.
