Four billion years ago, Uranus and Neptune switched places during a gentle ride out to their current orbits. That's the conclusion of Steve Desch, an astrophysicist at Arizona State University, who thinks that all of the gas giant planets took shape twice as close to the sun as they are at present. His work could cut out much of the mystery of how our "impossible" solar system formed. picked by AutumnLotus 8 months ago