The faint young Sun problem
The Sun shines a quarter dimmer than today, yet Earth has liquid oceans — and nobody fully knows why.
- When
- Known to
- ± 100 million years
- Era
- Eoarchean, Archean
Stellar models require the early Sun to have been roughly 70% as luminous as now, which should have left Earth frozen solid. The rocks say otherwise: oceans, sediments and life are all present. Extra greenhouse warming from carbon dioxide and methane is the usual explanation, possibly helped by fewer clouds and darker seas. The mismatch between theory and evidence has stood since the 1970s.