# Copenhagen interpretation

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The Copenhagen interpretation is an interpretation of quantum mechanics. Quantum mechanics postulates that the state of every particle can be described by a wavefunction, which is a mathematical representation used to calculate the probability that the particle is found to be in a location or a state of motion. According to this interpretation, the act of measurement causes the calculated set of probabilities to "collapse" to the value defined by the measurement. This feature of the mathematical representations is known as wavefunction collapse. The Copenhagen interpretation consists of attempts to explain the experiments and their mathematical formulations. It was formulated by Niels Bohr, Werner Heisenberg and others in the years 1924-1927. They stepped beyond the world of empirical experiments and pragmatic predictions of such phenomena as the frequencies of light emitted under various conditions. In the earlier work of Planck, Einstein and Bohr himself, discrete quantities of energy had been postulated in order to avoid paradoxes of classical physics when pushed to extremes. Bohr and Heisenberg now found a new world of energy quanta, entities that fit neither the classical ideas of particles nor the classical ideas of waves. Elementary particles showed predictable properties in many experiments. But they became highly unpredictable in certain contexts, for example if one attempted to measure their individual trajectories through a simple physical apparatus.

The Copenhagen interpretation is a composite statement about what can be legitimately stated in common language to complement the statements and predictions that could be made in the language of instrument readings and mathematical operations. In other words, it attempts to answer the question, "What do these amazing experimental results really mean?". The insight that quantum mechanics does not yield an objective description of microscopic reality but that measurement plays an ineradicable role is probably the most telling characteristic of the Copenhagen interpretation. The new theories were inspired by laboratory experiments and based on the idea that matter has both wave and particle aspects. One of the consequences, derived by Heisenberg, was that knowledge of the position of a particle limits how precisely its momentum can be known – and vice-versa.