The Faint Young Sun Paradox

The Faint Young Sun Paradox describes the contradiction between evidence for liquid water on early Earth and astrophysical models showing the sun was about 30% dimmer billions of years ago. A weaker sun should have kept Earth frozen, yet geological records show it was warm and wet. The leading explanations involve a stronger greenhouse effect, possibly from high levels of methane or carbon dioxide, but the precise resolution remains an active scientific debate.