Hafele-Keating Experiment

The Hafele-Keating Experiment tested Einstein's theory of relativity by flying atomic clocks around the world on airplanes. When compared to clocks that stayed on the ground, the airborne clocks showed slight time differences. These differences matched the predictions of relativity: moving clocks run slower due to their motion (special relativity), and clocks at different gravitational potentials run at different rates (general relativity). This experiment provided practical proof that time is affected by both motion and gravity, confirming Einstein’s theories through real-world measurements.