4 ms·
Funny argument when one realizes that QED, formulated well after 1920, is one of the most tested theories with the best quantitative results currently, with agr
by davrosthedalek 4y ago
Funny argument when one realizes that QED, formulated well after 1920, is one of the most tested theories with the best quantitative results currently, with agreement between experiment and theory to better than 10^-12 relative precision (depending how you count) for g_e/2.
- adrian_b 4y agoQED is very well tested for the handful of values that can be computed accurately (with great efforts). These special values are too few to matter for practical applications and they apply only to exceedingly simple systems, e.g. a single free lepton or a single pair of interacting elementary particles. The practical value of QED is null. By far the greatest success of QED is what you have mentioned, i.e. that it explains why g_e is not exactly 2, but it is slightly different. This fact could not be explained by the Dirac theory. However, we already knew the value of g_e through experiments. Having an explanation for our peace of mind is good, but this cannot help us design anything. For example, it would have been enormously helpful if there would have existed any method to compute accurately the frequencies and various other properties of the spectral lines of the atoms and ions. This would have allowed e.g. to find through computation optimal substances for applications like lasers and atomic clocks. Because there exists no such method, the advances continue to be done only by discovering through experiments new better spectral transitions of certain atoms or ions.