Imagine a beacon built by some ancient civilization that goes silent long before we humans learned to craft telescopes or point a radio dish at the sky.
Could we ever have known it existed?
The questions about timing, survival, and cosmic bad luck is at the heart of what Amedeo Balbi presented at IAUS404: Advancing the Search for Technosignatures in March 2026.
About the Presenter
Amedeo Balbi is an Associate Professor of Astronomy and Astrophysics in the Physics Department at the University of Rome Tor Vergata, where his research spans cosmology, theoretical physics, and astrobiology.
Over the past several years he has become one of the more prominent theorists working on the statistical and physical constraints on technosignature searches, often in collaboration with physicists. His past work includes a study of how the Milky Way’s central supermassive black hole may affect galactic habitability, and more recent papers exploring what atmospheric chemistry and thermodynamics can tell us about which planets could plausibly host detectable technology.
More About Balbi’s Work in Advancing the Search for Technosignatures
Balbi’s talk asked a deceptively simple question: given that any signal we detect must have had time to reach us, what does that “causal” requirement imply about the technosignatures we’re likely to find?
Because the galaxy is old but comparatively small (light crosses it in about 100,000 years), a technosignature has to persist for a long time to have any chance of overlapping with our brief window of observation. Reframing the Drake equation as a queuing problem, Balbi showed that detectability depends on just two numbers: how often technosignatures appear, and how long each one lasts, and that simulations consistently favor extremely long-lived signals, ones persisting for hundreds of millions of years, unless a short-lived signal happens to appear almost exactly when we do.
He also explored whether technosignatures might follow “Lindy’s law,” the pattern seen in technologies (rather than living things) where the old are more likely to persist than the young, and showed how physical limits, such as the atmospheric oxygen needed for open-air fire, and the waste heat inevitably produced by exponential energy growth, constrain how far any technosphere can climb before threatening its own planet’s habitability.
Key Takeaways
A technosignature is only detectable if its signal has had time to reach us, a basic constraint that biases searches toward extremely long-lived signals.
Reframing the Drake equation as a “birth rate × duration” problem shows that longevity, not the rate of civilizations appearing, is usually the dominant factor in detectability.
Random-distribution simulations show that unless a technosignature is almost perfectly synchronized with our own moment in time, it needs to last hundreds of millions of years to be observable today.
Physical limits, atmospheric oxygen for fire, and waste heat from exponential energy growth, may cap how advanced (and how long-lived) a planet-bound technosphere can become.
This kind of demographic reasoning connects to a wider push in technosignature science to treat non-detection itself as data. A closely related poster at the same symposium, from Balbi’s frequent collaborator Claudio Grimaldi, showed that sixty years of silence already constrains how common and how long-lived technosignatures could be. More recently, a 2026 preprint testing the Kardashev growth model against six decades of real-world energy data has begun engaging directly with the waste-heat limits Balbi described.
This video was included in the proceedings of the International Astronomical Union (IAU) symposium #404, Advancing the Search for Technosignatures, hosted by Blue Marble Space.
Thanks for joining us here with Planetary Perspectives, an editorial endeavor and science communication project from Blue Marble Space.
