Stephen Hawking is the most famous scientist on the planet. His popular science book A Brief History of Time was a publishing sensation, staying at the top of the bestseller lists longer than any other book in recent history. But behind the public face lies an argument that has been raging for almost 30 years.
Hawking shot to fame in the world of physics when he provided a mathematical proof for the Big Bang theory. This theory showed that the entire universe exploded from a singularity, an infinitely small point with infinite density and infinite gravity. Hawking was able to come to his proof using mathematical techniques that had been developed by Roger Penrose. These techniques were however developed to deal not with the beginning of the Universe but with black holes.
Science had long predicted that if a sufficiently large star collapsed at the end of its life, all the matter left in the star would be crushed into an infinitely small point with infinite gravity and infinite density - a singularity. Hawking realized that the Universe was, in effect, a black hole in reverse.
Instead of matter being crushed into a singularity, the Universe began when a singularity expanded to form everything we see around us today, from stars to planets to people. Hawking realized that to come to a complete understanding of the Universe he would have to unravel the mysteries of the black hole.