IvesStilwellexperimentet

The Ives–Stilwell experiment is a classic test of special relativity conducted in 1938 by Herbert E. Ives and George Stilwell. It was designed to probe time dilation, a central prediction of Einstein’s theory, by measuring the transverse Doppler effect in light emitted by fast-moving atoms or ions.

In the experiment, a beam of fast-moving atoms or ions was produced and excited to emit light. The researchers observed the emitted photons in directions both along and opposite to the beam. By comparing the observed frequencies with the known rest-frame frequency, they could isolate the relativistic time-dilation contribution to the Doppler shift, which for transverse emission reduces the observed frequency by a factor of gamma (1/γ).

The method relied on precise spectroscopic measurements of the light’s frequency from the moving source and careful calibration against a stationary reference. The forward and backward observations provided a way to separate the standard Doppler shift from the time-dilation component predicted by special relativity.

Results from the Ives–Stilwell experiment were consistent with the relativistic prediction, offering one of the early direct confirmations of time dilation. The work demonstrated that time dilation is an observable consequence of velocity in flat spacetime and reinforced the broader acceptance of special relativity in the physics community.

Significance of the study lies in its direct measurement of the transverse Doppler effect, complementing other tests of relativity. It inspired later, more precise experiments and remains a frequently cited example of empirical support for time dilation and the Doppler effect in high-velocity regimes.