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Heisenberg’s uncertainty principle

An example for such complementary quantities are the location and the momentum of a quantum particle: Very precise determination of the location make precise statements about its momentum impossible and vice versa.

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uncertainty principle

See Heisenberg's uncertainty principle

momentum

Physical quantity that is equal to a body's mass times its velocity (in special relativity: its relativistic mass times its velocity). What makes momentum a useful quantity is that it is conserved - if several bodies interact, the sum of their momenta before and after the interaction is the same. Momentum is neither created nor destroyed, merely passed on from one body to another. In general relativity, momentum is one of a number of quantities (like mass and energy) that acts as a source of gravity.

law of (inertia)

Basic law of classical mechanics and special relativity: bodies on which no external forces act move with constant speed on straight paths. In the geometrical language of special relativity, this can be reformulated as: bodies on which no external forces act move on straight line in spacetime. Strictly speaking, though, this law is only true in specific reference frames. This gives rise to a further, more precise reformulation: It is always possible to find a reference frame on which bodies on which no external forces act move with constant speed along straight paths. Such reference frames are called inertial frames. In general relativity, the law of inertia holds in a somewhat modified form: there, bodies on which no external, non-gravitational forces act don't move on straight lines through spacetime, but on geodesics.

Heisenberg's uncertainty principle

Is a fundamental law of quantum theory, which defines the limit of precision with which two complementary physical quantities can be determined. If one of the quantities is measured with high precision, the corresponding other quantity can necessarily only be determined vaguely. In other words, it is impossible to measure simultaneously both complementary quantities with greater precision than the limit defined by the Heisenberg's uncertainty principle. An example for such complementary quantities are the location and the momentum of a quantum particle: Very precise determination of the location make precise statements about its momentum impossible and vice versa.

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Heisenberg’s uncertainty principle

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