Some two billion years ago, all of Earth may well have been covered in snow and ice. Oceans, continents, everything, and for many millions of years. Observed from afar, the planet would be pretty low on the list of planets that might conceivably support life. But we know that it did. Five hundred to seven …
Exoplanet Earth
Some two billion years ago, all of Earth may well have been covered in snow and ice. Oceans, continents, everything, and for many millions of years. Observed from afar, the planet would be pretty low on the list of planets that might conceivably support life. But we know that it did. Five hundred to seven …
Many Worlds 