Werner Karl Heisenberg (1901-1976), German physicist. Heisenberg was awarded the 1932 Nobel Prize in Physics for his work on a matrix theory of quantum mechanics. It was a dualistic theory, meaning that phenomena could be described either in terms of waves or in terms of the new quanta (particles). In 1927, Heisenberg had stated his uncertainty principle (represented here by the question mark above his head and on his tie) that a particle's momentum and position cannot both be determined. This means that subatomic events depend on probabilities. Heisenberg was awarded the German Physical Society's Max Planck Medal in 1933.