Science fiction author Arthur C. Clarke once said, “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” A new analysis by a NASA researcher suggests there may be a third option, one that is less terrifying but far more sobering. According to astrophysicist Robin Corbet of NASA’s Goddard Space Flight Center, extraterrestrial civilizations might exist, but they are neither advanced empire builders nor mysterious overseers. They could be ordinary societies that hit a ceiling in their technological development long ago and decided to stop trying to reach anyone at all.

Corbet’s paper, released on the preprint archive arXiv in late September 2025, is titled A Less Terrifying Universe? Mundanity as an Explanation for the Fermi Paradox. In it, he proposes a principle of “radical mundanity,” the idea that the most unremarkable explanation for the apparent absence of aliens is probably the right one. Instead of vast galactic federations or transcendent intelligences, the Milky Way might contain a modest number of civilizations much like our own, limited by physics, resources, and motivation. They never built Dyson spheres or interstellar colonies because those things were never practical or necessary.

The Fermi Paradox has puzzled scientists for seventy-five years. Statistically, the galaxy should be full of intelligent life. With hundreds of billions of stars, many hosting planets, even conservative estimates suggest that at least a few should have developed technology millions of years before humanity appeared. Yet no radio signals, megastructures, or credible artifacts have ever been detected. Enrico Fermi summed it up during a lunch in 1950 with the question that defined the problem: “Where is everybody?”

Corbet argues that the answer lies not in mystery but in mathematics. Civilizations arise, develop energy-intensive technologies, and plateau when they reach the limits of what is physically or ecologically sustainable. They continue to exist for long periods, but their capacity for galaxy-scale engineering never materializes. As a result, no civilization builds beacons powerful enough to announce itself over interstellar distances, and no fleets of probes sweep the sky. The universe remains quiet, not because it is empty, but because its inhabitants stopped shouting.