The antiproton (p, pronounced p-bar) is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived since any collision with a proton will cause both particles to be annihilated in a burst of energy. It was discovered in 1955 by University of California, BerkeleyphysicistsEmilio Segrè and Owen Chamberlain, for which they were awarded the 1959 Nobel Prize in Physics. An antiproton consists of two up antiquark and one down antiquark (uud). The properties of the antiproton that have been measured all match the corresponding properties of the proton. The question of how matter is different from antimatter remains an open problem, in order to explain how our universe survived the Big Bang and why so little remains of antimatter today in our solar system.