A researcher from the Federal Polytechnic School of Lausanne has proposed a statistical model that makes it possible to more efficiently assess the likelihood of finding advanced alien civilizations.
Could there be another planet in the Universe with a society at the same level of technological development as ours? To find out, EPFL scientist Claudio Grimaldi worked with the University of California at Berkeley to develop a statistical model that provides researchers with a new tool for finding signals that might be emitted by an extraterrestrial community. This method, described in an article published in the journal Proceedings of the National Academy of Sciences, can make searches more efficient and accessible.
Since the late 1950s, there have been several projects to search for extraterrestrial intelligence, mostly in the United States. The idea was that an advanced civilization on another planet could generate electromagnetic signals, and scientists on Earth could pick up those signals with the latest high-performance radio telescopes.
Despite major advances in radio astronomy and computer technology, none of these projects have yielded concrete results. Some signals without a specific source were recorded in 1977 as Wow! Signals, but none of them were repeated or reliable enough to be attributed to alien life.
Schematic representation of the Milky Way with six isotropic signals forming spherical shells filled with radio signals. The outer radius of the shells is proportional to the time of the first signal, and the thickness is proportional to the duration of transmissions / © Claudio Grimaldi / EPFL
Today, more sophisticated instruments are being developed, such as the giant Square Kilometer Array radio telescope in South Africa and Australia, as well as the Breakthrough Listen program announced by Russian entrepreneur Yuri Milner. It aims to cover an area of the sky ten times more than in previous studies. This area will be scanned over a wider range of frequencies. Milner intends to invest $ 100 million in the initiative in ten years.
“In fact, expanding our search to such values only marginally improves our chances of finding something. And even if we do not register any signals then, we will still not be able to conclude with certainty that there is no life anywhere else,”says Grimaldi.
The advantage of the Grimaldi statistical model is that it allows scientists to interpret both success and failure in recording signals at different distances from the Earth. His model uses Bayes' theorem to calculate the residual probability of signal detection within a certain radius around our planet.
For example, even if no signal is detected within a thousand light-years, there is still a more than 10 percent chance that the Earth is within hundreds of similar signals from elsewhere in the galaxy, but our radio telescopes are simply not powerful enough to capture them. However, this probability rises to almost 100 percent if even one signal is detected within a radius of a thousand light years. In this case, we can be almost sure that the Galaxy is filled with life.
Given other parameters such as the size of the Milky Way and how close the stars are to each other, Grimaldi suggests that the probability of detecting a signal is very small within a radius of 40 thousand light years. In other words, if no signals are recorded at this distance from the Earth, we can conclude that there is no other civilization in the Galaxy with the same level of development. So far, scientists have had the ability to search for signals within a radius of only 40 light years. It should be borne in mind that in the Milky Way there may be civilizations with a lower level of development or, conversely, more developed, but following a different technological trajectory.