Supernova
Comets: Beyond the Atmosphere
1572 AD HVEN ISLAND, DENMARK Just how far away are comets? The Greek philosopher Aristotle said they were disturbances in the atmosphere, but the great Danish astronomer Tycho (pronounced "TY-koh") Brahe proved him wrong. Copernicus had recently begun the revolution that would let us understand the universe, by showing that the Earth was not the [...]