The Silence Paradox Just Got Louder
Since 1960, humanity has pointed radio telescopes, optical sensors, and infrared detectors skyward in search of alien technology. The SETI program has scanned for artificial transmissions, laser pulses, and waste heat signatures from advanced civilizations across the Milky Way. The result: nothing confirmed. A new theoretical study from EPFL physicist Claudio Grimaldi suggests we've been asking the wrong question. Rather than where are the aliens, he asks: if they've already tried to reach us and we missed it, what does that tell us about where to look next?
The findings, published in The Astronomical Journal, challenge a widespread assumption among SETI researchers—that past undetected signals mean better detections are coming soon. Instead, Grimaldi's statistical analysis suggests the opposite: if we haven't picked up technosignatures by now, any alien civilizations trying to contact us are probably far away, long-dead, or vanishingly rare.
The Detection Paradox: Two Conditions, One Big Problem
A technosignature—any measurable sign of advanced alien technology—faces a brutal mathematical gauntlet. For us to detect it, two things must occur: the signal must physically reach Earth, and our instruments must be sensitive enough to catch it, pointed in the right direction, and capable of filtering it from cosmic noise. A signal can clear the first hurdle and fail the second completely. It could be too weak, too brief, broadcast on the wrong frequency, or buried in background radiation.
This is where past "misses" become theoretically plausible. Over 66 years of searching, perhaps dozens—or thousands—of alien broadcasts have passed through Earth's neighborhood unnoticed. The catch? Grimaldi's analysis suggests this scenario creates a mathematical absurdity.
The Math That Breaks the "They're Close" Theory
Grimaldi used Bayesian statistics to link three variables: the number of technosignals that must have reached Earth since 1960, the lifespan of those signals (ranging from days to millennia), and the detection range of current and near-future instruments. He modeled both omnidirectional broadcasts—like waste heat radiating from megastructures—and focused beams such as laser communications or intentional beacons.
The results are sobering. For us to have a high probability of detecting a technosignature within a few hundred to a few thousand light-years today, the number of signals that must have passed through Earth undetected becomes implausibly large. In many scenarios, it exceeds the total number of potentially habitable planets in that entire region of the galaxy. Translation: we'd need more aliens sending signals than there are planets to send them from.
This doesn't prove aliens don't exist. It proves that if they do and they've contacted us, they're probably not in our cosmic neighborhood.
The Search Gets Deeper, Not Longer
The study's implications reshape SETI strategy. Grimaldi's analysis suggests that detectable technosignatures, if they exist at all, are most likely from distant sources several thousand light-years away—far beyond our galactic suburbs. These would be rare, long-lived signals, not frequent broadcasts from nearby civilizations.
This reframes the search as a patient, generational effort rather than a waiting game for obvious signals. It strengthens the case for deep, wide surveys that scan massive portions of the Milky Way instead of focusing on nearby star systems. Projects like FAST (the Five-hundred-meter Aperture Spherical Telescope) and next-generation radio arrays will be crucial, but expectations should shift: we're not listening for neighbors knocking on the door. We're looking for faint, distant echoes from the cosmic frontier.
The silence, it turns out, may be telling us something important about what kind of universe we actually live in.





