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The Copenhagen interpretation is an expression of the meaning of quantum mechanics that was largely devised in the years 1925 to 1927 by Niels Bohr and Werner Heisenberg. It remains one of the most commonly taught interpretations of quantum mechanics. According to the Copenhagen interpretation, physical systems generally do not have definite properties prior to being measured, and quantum mechanics can only predict the probabilities that measurements will produce certain results. The act of measurement affects the system, causing the set of probabilities to reduce to only one of the possible values immediately after the measurement. This feature is known as wavefunction collapse. There have been many objections to the Copenhagen Interpretation over the years. Some have objected to the discontinuous jumps when there is an observation, or the probabilistic element introduced upon observation; or to the subjectiveness of requiring an observer; or to the difficulty of defining a measuring device; or to the necessity of invoking classical physics to describe the "laboratory" in which the results are measured. Alternatives to the Copenhagen Interpretation include the many-worlds interpretation, the De Broglie-Bohm (pilot-wave) interpretation, and quantum decoherence theories. ==Background== In the early work of Max Planck, Albert Einstein, and Niels Bohr, the occurrence of energy in discrete quantities was postulated in order to explain phenomena such as the spectrum of black-body radiation, the photoelectric effect, and the stability and spectrum of atoms. These phenomena had eluded explanation by classical physics and even appeared to be in contradiction with it. While elementary particles show predictable properties in many experiments, they become thoroughly unpredictable in others, such as attempts to identify individual particle trajectories through a simple physical apparatus. Classical physics draws a distinction between particles and waves. It also relies on continuity, and on determinism, in natural phenomena. In the early twentieth century, newly discovered atomic and subatomic phenomena seemed to defy those conceptions. In 1925–1926, quantum mechanics was invented as a mathematical formalism that accurately describes the experiments, yet appears to reject those classical conceptions. Instead, it posits that probability, and discontinuity, are fundamental in the physical world. Classical physics also relies on causality. The standing of causality for quantum mechanics is disputed. Quantum mechanics cannot easily be reconciled with everyday language and observation. Its interpretation has often seemed counter-intuitive to physicists, including its inventors. The Copenhagen interpretation intends to indicate the proper ways of thinking and speaking about the physical meaning of the mathematical formulations of quantum mechanics and the corresponding experimental results. It offers due respect to discontinuity, probability, and a conception of wave–particle dualism. In some respects, it denies standing to causality. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Copenhagen interpretation」の詳細全文を読む スポンサード リンク
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