Imagine a world frozen solid. Imagine that vast sheets of ice hundreds of feet thick encased the entire planet--a giant snowball floating through space. This is not some exotic new world deep in space. It may be our world, the Earth. Some top-ranking scientists believe that in the past the Earth froze over completely for millions of years... then warmed up rapidly over 600 million years ago. Struggling against skepticism and disbelief for years, they have gathered a growing body of evidence that explains many mysteries, and others in the scientific community are slowly coming around to the extraordinary idea not just of the dramatic freeze, but of an equally dramatic thaw. Naked Science explores what may have been the most extreme period of Earths climatic history, Meeting all the major players of this controversial theory that is Snowball Earth.