The instability at the beginning of the solar system

Michigan State University's Seth Jacobson and colleagues in China and France have unveiled a new theory that could help solve a galactic mystery of how our solar system evolved. Specifically, how did the gas giants -- Jupiter, Saturn, Uranus and Neptune -- end up where they are, orbiting the sun like they do? The research also has implications for how terrestrial planets such as Earth were formed and the possibility that a fifth gas giant lurks 50 billion miles out into the distance.