The Sun Was 30% Dimmer When Life Began — So Why Didn't Earth Freeze?

Four billion years ago, the Sun shone thirty percent dimmer than it does today. Every climate model gives the same answer: Earth should have been permanently frozen, the oceans locked under ice, life impossible. And yet the oldest rocks on Earth show liquid water. Life was already present. The paradox has been known since Carl Sagan named it in 1972. Fifty years of research have produced a rich collection of partial answers — elevated methane from ancient microbes, a darker ocean-dominated planet, a closer Moon providing tidal heat, a geological thermostat running in the background — but no single clean solution. And new research published in 2025 and 2026 is still adding pieces to the puzzle. This episode tells the complete story: the physics, the geology, the biology, and why the paradox is still not fully solved. SUBSCRIBE    / @chroniclesplanetearth   for deep science at the edge of what we know.