If you were teleported back in time some 700 million years ago inside a spaceship overlooking our planet, the sight would be shocking. Instead of a marvelous blue marble, you’d see a glistening white ball. During this highly dramatic episode of Earth’s geologic history, scientists think that ice smothered the entire planet — from the poles to the equator. Temperatures were far below freezing virtually at every point on the globe. When Caltech geologist Joe Kirschvink coined the term Snowball Earth in 1989 to describe what the geological evidence pointed to, many experts were left in disbelief….
