BBC Documentaries - 2007x09 - The Comet's Tale- Followmy.tv

Although believed to be gods by many ancient civilisations, who saw them as bringers of life or harbingers of doom, to Isaac Newton they were the key to unlocking the secrets of gravity. Hundreds of years later, a new breed of space mission can show what comets are really made of, where they come from, and their surprising influence on events on Earth.