Oliver Cecil Simpson (1909–2002)

Oliver Cecil Simpson coauthored atomic-beam measurements using gravitational free fall to investigate the velocity distribution of cesium atoms. Gravity makes a particle's displacement depend on its travel time, so slower atoms are deflected more during a given path. For an ideal horizontal flight of length $L$ at speed $v$, the downward displacement is $g{L}^2/(2v^2)$. The measurement connects a beam's spatial distribution with its microscopic velocities, using gravity as a timing-dependent probe.^[ref]

Physics and solid state science.^[ref]