The Sun as a gravitational lens to communicate with extraterrestrial civilizations

When NASA shared the first deep-field image starring the group of galaxies called SMACS 0723 at the center, all astronomy enthusiasts jumped in their chairs for the incredible detail and the very large number of celestial bodies and visible gravitational lenses.

If SMACS 0723 is located about 4.6 billion light years from our point of view, thanks to the gravitational lensing effect we have been able to observe galaxies positioned up to 13.1 billion light years from us. The gravitational lens effect, in full agreement with the theory of general relativity, predicts that large celestial bodies such as black holes and groups of galaxies, are able to bend the trajectory of passing light in a similar way to what an optical lens would do. (you can see an example in the header), and some believe that this property can also be exploited with smaller celestial bodies.

Einstein’s theory of general relativity tells us that the gravitational pull of huge celestial objects can bend light. When it does, it focuses and magnifies the light of objects behind it like a telescope would, achieving the effect called gravitational lens.

For example, let’s think of our Sun and try to imagine finding a way to use it as a gravitational lens for the observation of other star systems and very distant exoplanets. We would have in our hands a sort of very powerful natural telescope that would open up to infinite possibilities of study.

But someone has gone even further by hypothesizing that this system could bring with it other advantages that, with our current technological development, we cannot currently exploit. But who said that other civilizations did not evolve before ours and were able to exploit gravitational lenses in ways we can now only imagine? This is what a group of graduates at Penn State University thinks, according to which communications could also enjoy this characteristic of space-time, and perhaps someone may have already set up a real interstellar communication network.

It is good to clarify right away that in this case the boundary between science and science fiction is really blurred, therefore we speak of hypotheses on which theories have been built. In short, the base is shaky but fascinating at the same time, so you need to have an open mind and free from preconceptions when reading news of this caliber.

But let’s get to the crux of the matter: During a SETI course on the search for extraterrestrial intelligence, the group of graduates suggested that gravitational lenses could also affect other processes besides visible light, and if this proves true, communications could also exploit in some way. way the phenomenon of amplification. If any particularly advanced civilization were able to exploit the gravitational lens caused by a star, too our Sun could be part of a large communication network over long distances. The operating principle could in some ways resemble that of cellular networks currently in use on Earth, as stated by Nick Tusay, one of the students involved in the research.

Humans use networks to communicate around the world all the time. When you use a cell phone, electromagnetic waves are transmitted to the nearest cell tower, which connects to the next tower and so on.

Imagine that a civilization has launched probes at specific locations in the vicinity of a star with the aim of exploiting its gravitational lens, and that these are used as connection points for a large communication network. What if our Sun was part of it? Probably even with our current technology we might be able to pick up something. And so, based on these assumptions, the group of students used the Green Bank Telescope, in West Virginia, looking for radio transmissions that may have been broadcast from star systems close to ours, with a specific focus on Alpha Centauri.

Once again the choice was made to monitor radio waves rather than optical ones, as they were considered the best way to send communications into space. Result? At the moment no signal has been identified, but hope is apparently not lost. The research, in fact, was limited to one night only and therefore did not provide a significant sample that would allow us to totally exclude the hypothesis of the gravitational lens as an interstellar communication system. The idea is therefore to try again in the future with longer time intervals.

Yet the phenomenon of the gravitational lens is not only fascinating, but is currently being examined by astronomers for the construction of new generation telescopes so powerful as to make James Webb pale, which one day perhaps will allow us to better observe the planets around distant stars. light years from us.