The Heisenberg Uncertainty Principle
Uncertainty is one of the best known implications of the
quantum revolution. In 1927 Heisenberg argued that key physical quantities
(e.g. position and momentum) are paired up in quantum theory. As a result, they
cannot be measured simultaneously to any desired degree of accuracy. Attempts
to increase the precision of one measurement result in less precise measures of
the other member of the pair.
Take an electron, for example. We might try to determine its
position by using electromagnetic radiation. Because electrons are so small,
radiation of very short wavelength would be necessary to locate it accurately.
However, shorter wavelengths correspond to higher energies. The higher the
energy of radiation use, the more the momentum of the electron is altered. Thus
any attempt to determine the location accurately will change the velocity of
the electron. Conversely, techniques for accurately measuring the velocity of
the electron will leave us in ignorance about its precise location.
Further discussion of the Uncertainty Principle can be found
in John Polkinghorne’s largely non-technical book The Quantum World.
The Significance of Uncertainty:
The conservative interpretation was that uncertainty was a
limitation imposed by our measuring techniques.
However, Heisenberg himself took a more radical view - that
this limitation is a property of nature rather than an artifact of
experimentation. This radical interpretation of uncertainty implies that
quantum mechanics is inherently statistical - it deals with probabilities
rather than well-defined classical trajectories. Such a view is clearly
inimical to classical determinism. See Shaking the Foundations: the implications
of quantum theory.
Email
link | Feedback | Contributed by: Dr.
Christopher Southgate
Source: God, Humanity and the
Cosmos (T&T Clark, 1999)
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