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:
“How should the world be luckier if this house,
Where passion and precision have been one
Time out of mind, became too ruinous
To breed the lidless eye that loves the sun?”
—William Butler Yeats (1865–1939)
“What is a novel? I say: an invented story. At the same time a story which, though invented has the power to ring true. True to what? True to life as the reader knows life to be or, it may be, feels life to be. And I mean the adult, the grown-up reader. Such a reader has outgrown fairy tales, and we do not want the fantastic and the impossible. So I say to you that a novel must stand up to the adult tests of reality.”
—Elizabeth Bowen (1899–1973)