Werner Heisenberg (1901–1976) was a German physicist who made significant contributions to quantum mechanics and is best known for formulating the Heisenberg Uncertainty Principle, a fundamental concept in quantum theory. This principle states that certain pairs of physical properties, like position and momentum, cannot both be precisely measured simultaneously.
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Werner Heisenberg's 1925 reformulation of quantum mechanics replaced unobservable classical electron orbits with quantities attached to transitions between stationary quantum states. Transition frequencies combine as , suggesting the indexed product rule that became matrix multiplication. The resulting physical quantities need not commute. This approach made measured spectral lines and transition strengths the starting data for a new dynamics rather than requiring a miniature classical planetary model of the atom.[ref]
On the quantum reinterpretation of kinematical and mechanical relationships by Werner Heisenberg. 1925 paper, transition quantities and their multiplication rule
Portrait of Werner Heisenberg
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Participated in the German nuclear weapons program, ouch.