Nonlocality

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Physical theories are said to exhibit nonlocality if it is not possible to treat widely separated systems as independent. Nonlocality does not necessarily imply a lack of causality. For instance, Newtonian gravitation is nonlocal because it involves action at a distance but Newtonian mechanics is certainly causal. Effects that appear nonlocal, but actually obey locality, appear in quantum mechanics. These effects are also referred to as "spooky action at a distance", and are closely related to Bell's theorem and the EPR paradox. Quantum field theory, the relativistic generalization of quantum mechanics, is necessarily local, so nonrelativistic quantum mechanics is local as well.

See also

• Principle of locality
• Nonlocal Lagrangian
• Bell's theorem