In 1962 Francis Everitt arrived at Stanford University as the first full-time staff member of Gravity Probe B (GP-B), a satellite-borne experiment conceived to test Albert Einstein’s general theory of relativity. A half century and $760 million later, Everitt announced at a NASA press conference in May, seven years after launch, that GP-B had completed its data analysis and Einstein’s magnum opus passed comfortably.1
If the experiment had run to spec, it would have measured with unprecedented precision two properties predicted by general relativity: the so-called geodetic and frame-dragging effects, which imply that an orbiting gyroscope will precess even when no external torque acts on it. Though Everitt and colleagues were able to confirm the geodetic effect with an impressive and currently standard-bearing error of 0.3%, they could only confirm frame dragging—a much smaller effect less well measured by independent efforts—to within 20%. Nonetheless, GP-B’s half-century-long experiment was a...
