One of the most valuable metals in the world, uranium's use has dramatically changed since its discovery in 1789. Originally used in the production of steel-alloys, uranium improved the strength and elasticity of steel without making it brittle. Since 1939 it's rarely been used for anything besides atomic energy. This heavy, white metal's greatest contribution is to the process of nuclear fission. Radioactive manipulation of uranium atoms can eject neutrons, which can travel at speeds up to 12,000 miles per second. If such a neutron impacts the nucleus of a neighboring atom, the target atom can completely fragment. Not only is the resulting energy released immense, but the shattered atom can also potentially collide with additional atoms. This chain reaction is the phenomenon underlying all nuclear fission applications including nuclear weapons and power.