The text book canon of quantum mechanics was formed by Bohr and Heisenberg in the 1920s and was named the Copenhagen Interpretation (CI) by Heisenberg in the 1950s.
Let us seek the origin and motivation behind the Copenhagen Interpretation in Heisenberg's confessional treatise The Physicist's Concept of Nature. We find the following basic beliefs of Heisenberg:
- Even in the ancient atomic theory of Democritus and Leucippus it was assumed that large-scale processes were the results of many irregular processes on a small scale.
- Thus we always use concepts which describe behaviour on the large scale without in the least bothering about the individual processes that take place on the small scale.
- Now, if the processes which we can observe with our senses are thought to arise out of the inter-actions of many small individual processes, we must conclude that all natural laws may be considered to be only statistical laws.
- Thus it is contended that while it is possible to look upon natural processes either as determinedby laws, or else as running their course without any order whatever, we cannot form any picture of processes obeying statistical laws.
- Planck, in his work on the theory of radiation, had originally encountered an element of uncertainty in radiation phenomena. He had shown that a radiating atom does not deliver up its energy continuously, but discreetly in bundles. This assumption of a discontinuous and pulse-like transfer of energy, like every other notion of atomic theory, leads us once more to the idea that the emission of radiation is a statistical phenomenon.
- However, it took two and a half decades before it became clear that quantum theory actually forces us to formulate these laws precisely as statistical laws and to depart radically from determinism.
- With the mathematical formulation of quantum-theoretical laws pure determinism had to be abandoned.