Cool indeed. Snowball Earth: Science grapples with a puzzling new theory: the extreme ice age. » "Even the scientists who first thought up the idea didn't think it was possible: That the entire Earth could have frozen over and been encased in a solid cover of snow and ice, perhaps for millions of years. ... Snowball Earth 'is an extreme example of an instability of the climate system', Hoffman said. 'As a geologist, the remarkable thing about the last 10,000 years is how remarkably stable the climate has been'.''