Precision Tests Of QED
Quantum electrodynamics (QED), a relativistic quantum field theory of electrodynamics, is among the most stringently tested theories in physics.
The most precise and specific tests of QED consist of measurements of the electromagnetic fine structure constant, α, in various physical systems. Checking the consistency of such measurements tests the theory.
Tests of a theory are normally carried out by comparing experimental results to theoretical predictions. In QED, there is some subtlety in this comparison, because theoretical predictions require as input an extremely precise value of α, which can only be obtained from another precision QED experiment. Because of this, the comparisons between theory and experiment are usually quoted as independent determinations of α. QED is then confirmed to the extent that these measurements of α from different physical sources agree with each other.
The agreement found this way is to within ten parts in a billion (10−8), based on the comparison of the electron anomalous magnetic dipole moment and the Rydberg constant from atom recoil measurements as described below. This makes QED one of the most accurate physical theories constructed thus far.
Besides these independent measurements of the fine-structure constant, many other predictions of QED have been tested as well.
Read more about Precision Tests Of QED: Measurements of The Fine-structure Constant Using Different Systems, Other Tests, See Also
Famous quotes containing the words precision and/or tests:
“Some authorities hold that the young ought not to lie at all. That, of course, is putting it rather stronger than necessary; still, while I cannot go quite so far as that, I do maintain, and I believe I am right, that the young ought to be temperate in the use of this great art until practice and experience shall give them that confidence, elegance and precision which alone can make the accomplishment graceful and profitable.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“Although she feeds me bread of bitterness,
And sinks into my throat her tiger’s tooth,
Stealing my breath of life, I will confess
I love this cultured hell that tests my youth!”
—Claude McKay (1889–1948)