In 1938, Otto Hahn and Fritz Strassman discovered that uranium nuclei could spit and form smaller nuclei, or different elements 1938, otto what process did Hahn and Strassman discover?
Nuclear fission! Or the source of the infamous atomic bombs. :(
I am not a physicist, but atomic fission is when a large nuclide is bombarded with neutrons, splitting into smaller and smaller nuclei and more and more neutrons which produces a chain reaction.
A critical mass is the mass required for a spontaneous, self-sustaining chain reaction used in nuclear power plants. A supercritical mass is one above the mass required, leading to violent, uncontrollable chain reactions (e.g. atomic bombs).