Back when the sun was 30% dimmer, Earth should have frozen solid. Yet water flowed and life blossomed. The solution to the paradox shows that we might have that faint sun to owe for life’s existence — with critical consequences for the possibility of life outside Earth.
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| In the early solar system, a close-orbiting moon would have contorted Earth’s interior, heating it from within. James O’Brien for Quanta Magazine |
