Quantum mechanics

For a non-technical introduction to Quantum Mechanics, please see Quantum Mechanics - simplified

Philosophical consequences

Since its inception, the many counter-intuitive results of quantum mechanics have provoked strong philosophical debate and many interpretations. Even fundamental issues such as Max Born's basic rules concerning probability amplitudes and probability distributions took decades to be appreciated.

Related Topics:
Philosophical - Interpretations - Max Born - Probability amplitude - Probability distribution

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The Copenhagen interpretation, due largely to Niels Bohr, was the standard interpretation of quantum mechanics when it was first formulated. According to it, the probabilistic nature of quantum mechanics predictions cannot be explained in terms of some other deterministic theory, and does not simply reflect our limited knowledge. Quantum mechanics provides probabilistic results because the physical universe is itself probabilistic rather than deterministic.

Related Topics:
Copenhagen interpretation - Niels Bohr - Deterministic

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Albert Einstein, himself one of the founders of quantum theory, disliked this loss of determinism in measurement. He held that there should be a local hidden variable theory underlying quantum mechanics and consequently the present theory was incomplete. He produced a series of objections to the theory, the most famous of which has become known as the EPR paradox. John Bell showed that the EPR paradox led to experimentally testable differences between quantum mechanics and local hidden variable theories. Experiments have been taken as confirming that quantum mechanics is correct and the real world cannot be described in terms of such hidden variables. "Loopholes" in the experiments, however, mean that the question is still not quite settled.

Related Topics:
Albert Einstein - Local hidden variable theory - EPR paradox - John Bell - Loopholes

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

See the Bohr-Einstein debates

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The Everett many-worlds interpretation, formulated in 1956, holds that all the possibilities described by quantum theory simultaneously occur in a "multiverse" composed of mostly independent parallel universes. While the multiverse is deterministic, we perceive non-deterministic behavior governed by probabilities because we can observe only the universe we inhabit.

Related Topics:
Everett many-worlds interpretation - 1956 - Multiverse

~ ~ ~ ~ ~ ~ ~ ~ ~ ~