# Werner Heisenberg German physicist who formulated matrix mechanics in 1925 at twenty-three and stated the uncertainty principle in 1927 (see Heisenberg Uncertainty). Co-author with [[Niels Bohr]] of the Copenhagen Interpretation. Nobel Prize in Physics, 1932. Heisenberg led Nazi Germany's nuclear weapons program and remained in Germany throughout the war. Whether he deliberately slowed the effort, misjudged the critical mass calculation, or simply failed is disputed by historians and unresolved by the Farm Hall transcripts — one of the twentieth century's more consequential open questions about a scientist's conduct under an authoritarian state.