Jan 20, 2021
In the late 1950’s, scientists at NASA and Stanford University devised an experiment to measure two relativistic effects of Earth’s mass and spin. If successful, the experiment would provide empirical validation of Einstein’s general theory of relativity, a tantalising prospect given the weak and insubstantial nature of these phenomena at low masses and energies.
At the heart of the design was a set of precisely calibrated gyroscopes which, when placed in orbit around the Earth, could detect the minute effects of frame-dragging and geodetic distortion caused by the curvature of spacetime. The “drift” due to Earth’s mass was predicted to be so subtle that the experiment had to be engineered to almost impossibly tight tolerances. To prevent noise or wobble dominating the measurements, each gyroscope had be one of the most perfectly round objects ever created by humans. After years of research and several technological leaps, the team finally succeeded in fabricating a small number of fused quartz spheres whose radii varied by no more than a few dozen atoms in any given direction.