What is "uncertainty principle"

n. (context quantum mechanics English) Heisenberg uncertainty principle.

n. (quantum theory) the theory that it is impossible to measure both energy and time (or position and momentum) completely accurately at the same time [syn: indeterminacy principle]

In quantum mechanics, the uncertainty principle, also known as Heisenberg's uncertainty principle, is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle, known as complementary variables, such as position x and momentum p, can be known.

Introduced first in 1927, by the German physicist Werner Heisenberg, it states that the more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa. The formal inequality relating the standard deviation of position σ and the standard deviation of momentum σ was derived by Earle Hesse Kennard later that year and by Hermann Weyl in 1928: ( is the reduced Planck constant, / ).

Historically, the uncertainty principle has been confused with a somewhat similar effect in physics, called the observer effect, which notes that measurements of certain systems cannot be made without affecting the systems. Heisenberg offered such an observer effect at the quantum level (see below) as a physical "explanation" of quantum uncertainty. It has since become clear, however, that the uncertainty principle is inherent in the properties of all wave-like systems, and that it arises in quantum mechanics simply due to the matter wave nature of all quantum objects. Thus, the uncertainty principle actually states a fundamental property of quantum systems, and is not a statement about the observational success of current technology. It must be emphasized that measurement does not mean only a process in which a physicist-observer takes part, but rather any interaction between classical and quantum objects regardless of any observer. (N.B. on precision: If δx and δp are the precisions of position and momentum obtained in an individual measurement and σ, σ their standard deviations in an ensemble of individual measurements on similarly prepared systems, then "There are, in principle, no restrictions on the precisions of individual measurements δx and δp, but the standard deviations will always satisfy σσ ≥ ℏ/2".)

Since the uncertainty principle is such a basic result in quantum mechanics, typical experiments in quantum mechanics routinely observe aspects of it. Certain experiments, however, may deliberately test a particular form of the uncertainty principle as part of their main research program. These include, for example, tests of number–phase uncertainty relations in superconducting or quantum optics systems. Applications dependent on the uncertainty principle for their operation include extremely low noise technology such as that required in gravitational-wave interferometers.

"Uncertainty Principle" is the second episode of the first season of the American television series Numb3rs. Based on a real bank robbery case, the episode features a Federal Bureau of Investigation (FBI) math consultant's prediction being incomplete after FBI agents find themselves in an unexpected shootout with suspected bank robbers. Series writers Cheryl Heuton and Nicolas Falacci wanted to explore the emotional effects of the case on Dr. Charlie Eppes ( David Krumholtz). For the mathematics used in the case, they included several mathematical and physics concepts, such as the Heisenberg uncertainty principle, P vs. NP, and Minesweeper.

The episode was directed by Davis Guggenheim and filmed in Los Angeles, California. Due to the type of scenes in the episode, filming took over nine days. During production, network executives objected both to the level of violence depicted in the episode and to the episodes plot. Guggenheim refused to tone down the violence, and Heuton and Falacci felt as though the points to which the executives objected served a purpose in the episode.

After being moved from fourth to second, "Uncertainty Principle" first aired in the United States on January 28, 2005. Critics gave the episode mixed reviews. One mathematician disliked the focus on the emotional reaction while critics liked the episode.

The uncertainty principle is a fundamental concept in quantum physics.

Uncertainty principle may also refer to:

• The Uncertainty Principle (film), a 2002 Portuguese drama
• "Uncertainty Principle" (Numb3rs), an episode of the TV series Numb3rs
• "The Uncertainty Principle" (The Spectacular Spider-Man), an episode of the TV series The Spectacular Spider-Man
• "The Uncertainty Principle", an episode of the TV series Holby City
• The Uncertainty Principle, a novel by Dmitri Bilenkin
• Principio de incertidumbre (Uncertainty principle), a novel by Gregorio Morales
• The French downtempo band Telepopmusik has a song titled "L'Incertitude D'Heisenberg" on their album Genetic World
• Uncertainty principle for the short-time Fourier transform, as related to frequency domain analysis of waveforms.