Where are the extraterrestrials? Perhaps they are unable to make contact with us.
In 1950, the renowned astrophysicist Enrico Fermi posed a profound question during an informal lunch with colleagues: where are they all? In other words, if there is an extremely high probability that advanced extraterrestrial civilizations exist somewhere, why haven’t we found evidence that they are out there? At least, that’s what the story goes. However, beyond the circumstances of that occasion, the question now known as the Fermi Paradox has captured the attention of researchers. In a not-yet-reviewed paper, astrophysicist Robin Corbet suggests that “radical mundanity” could be a possible explanation.
Corbet, a research scientist at the University of Maryland, Baltimore County, based at NASA’s Goddard Space Flight Center, proposes that the galaxy hosts a modest number of extraterrestrial civilizations that are not much more advanced than our own. As their technology has similar limitations, civilizations fail to make contact. “The idea is that they are more advanced, but not by much. It’s like having an iPhone 42 instead of an iPhone 17,” Corbet told. “It’s something that is perceived as more plausible and more natural, because it doesn’t propose anything too extreme.”
Alternative Explanation to the “Great Silence”
Calculations using the Drake Equation – a formula that calculates the number of Milky Way civilizations capable of transmitting radio signals – suggest that there should be some. Our civilization has been emitting radio signals for decades, so we know that the Drake Equation has at least one answer. Astrophysicists have proposed that it would take little time, on astronomical scales, for advanced civilizations to spread throughout the galaxy. If aliens were to achieve this feat, humanity should be able to detect their presence through different techno signatures that could include artificial electromagnetic rays, astroengineering signals like heat emanating from Dyson spheres (hypothetical megastructures that collect energy around stars), or extraterrestrial artifacts on Earth. But so far, we have found none of that.
Astrophysicists have put forward many different hypotheses to explain the lack of evidence that has been dubbed “the great silence.” Perhaps intelligent extraterrestrials are too advanced for humans to detect. Or maybe they choose to stay away from Earth. Are we alone in the galaxy, after all? Or perhaps, most pessimistically, all civilizations advanced enough end up destroying themselves. Corbet believes that all these possibilities are extreme, which is why he poses a different question: What if civilizations have a natural technological limit that prevents them from being so advanced as to create detectable techno signatures, or to detect us?
A Galaxy More Boring Than We Think
According to Corbet’s hypothesis, humanity could be close to its maximum technological progress limit. Alien civilizations could reach a similar ceiling, without advancing enough to be able to detect or make contact with other civilizations. The idea, known as the principle of radical mundanity, suggests that extraterrestrial societies do not build massive space structures or travel at the speed of light. Rather, they are likely to be like us and have the same limitations in detecting others in the galaxy. This remains the case for a long time, and eventually they lose interest in exploring the cosmos.
Even if the hypothesis is correct, that does not mean we will never find evidence of an extraterrestrial civilization. In his work, Corbet explains that a technologically mundane world could be detected through leaked radiation, and that this discovery “may not be far off” if radio telescopes continue to advance and improve. However, there is no need to get too excited, because Corbet comes to a conclusion: “Although this would have profound implications in many aspects, it may not represent a huge gain in our level of technology, and we might be somewhat disappointed.”
