Skip to content
Fellows Directory

Francis Farley

Professor Francis Farley FRS


Elected: 1972


Francis Farley has measured with great accuracy the anomalous magnetic moment of the muon, which has led to a marked extension toward short distances and high-momentum transfers of the verified range of validity of quantum electrodynamics. For this purpose, he has developed ingenious methods for the storage of muons in a magnetic field. He has made important contributions also to the accurate determination of other properties of the muon, to the study of cosmic rays, nuclear reactions and cloud formation and to the development of fast counting methods. Francis’ work on the velocity of gamma rays emitted in the decay of pi-to-infinity mesons has led to an accurate verification of the second postulate of special relativity for source velocities near the velocity of light while a by-product of his work on the storage of muons has led to the establishment of the relativistic time dilation effect (so-called clock paradox) for accelerated systems.

Interests and expertise

Subject groups


  • Hughes Medal

    For his ultra-precise measurements of the muon magnetic moment, a severe test of quantum electrodynamics and of the nature of the muon.