We compare the results of precision electron $g$-factor experiments at low energy and at 110 keV. The agreement between these measurements constitutes the most precise laboratory confirmation to date of the predictions of special relativity. Relativistic electromagnetic theory and Thomas precession are verified in this test. We also consider limits on possible effects of acceleration.

• Received 17 January 1978

DOI:https://doi.org/10.1103/PhysRevLett.40.1355