Scientists are claiming a stunning discovery in their quest to fully understand gravity. They have observed the warping of space-time generated by the collision of two black holes more than a billion light-years from Earth. It is the culmination of decades of searching and could ultimately offer a window on the Big Bang. Dr. Shane Larson is an astronomer for Adler Planetarium, Northwestern University and he was a part of the team that made the discovery. He joined John to explain what it all means.