QUANTUM MECHANICS

Famously described by one of its founders, Wolfgang Pauli, as being Knabenphysik (‘boys’ physics’), quantum mechanics abandoned classical determinism and effected an upheaval in scientific thought and epistemology even greater than that of Albert Einstein's RELATIVITY. Quantum theory first emerged in 1900 when Max Planck discovered that light energy is emitted in discrete units, or ‘quanta’, and not as a wave. The incompatibility of this behaviour with the laws of classical physics troubled the conservative Planck but would later be embraced, in the decade following World WAR I, by a new wave of younger, predominantly German-speaking, physicists. The pre-eminent centres for research in theoretical physics in the 1920s were Niels Bohr's institute in Copenhagen and the universities of Göttingen, Zurich and Berlin. There, amidst the troubled and unstable zeitgeist of post-war Europe, quantum theory was given a formalised mechanics and science a crisis of its own.

Marking quantum mechanics as an especially radical development in thought, and causing many (including Einstein) to have difficulty accepting it, was its move away from determinism and local causality. The standard, or ‘Copenhagen’, interpretation of quantum mechanics, presented at the 1927 Fifth Solvay International Conference, concerns a probabilistic mechanics and imposes theoretical limits on our ability to fully describe subatomic phenomena. Central to the Copenhagen interpretation are Bohr's principle of complementarity and Werner Heisenberg's uncertainty principle. Complementarity posits that differing observational results of the same phenomena need not be held as being mutually exclusive; accordingly, light can be described best in terms of a ‘wave-particle duality’. In addition to this, Heisenberg's principle states that the more accurately you determine either the position or momentum of a particle the less you can determine about the other. This is due, in part, to the influence of the act of measurement upon the system observed. The questions being posed by quantum theory were, then, in many respects, as much philosophical as they were physical; the epistemological foundations of science itself were being challenged.

Quantum mechanics experienced a less sensational public reception than relativity but it still had a notable influence upon contemporary culture of the time and captured the imagination of numerous members of the modernist AVANT-GARDE.