File: 10 October 2026 · Source date: 10 October 2026
Two relativity effects
General relativity predicts that the Earth's mass bendsspace-time and its rotation drags local inertial frames by a very small amount. The second effect is known as frame drift.
Measurement with gyroscopes
Gravity Probe B compared the change in direction of four highly sensitive gyroscopes in polar orbit to a distant guide star. The results confirmed the geodetic effect with high accuracy and frame drift with greater uncertainty.
Why was it difficult?
Magnetic effects, surface imperfections, and data modeling made it difficult to separate the small signal. The experiment showed that precise measurement requires clear calculation of systematic errors, not just good sensors.
discussion question
How would our understanding of motion change if we could feel the drift of space-time on a daily scale?
Resources and further reading
Physical Review Letters — Gravity Probe B: Final Results ↗NASA — Gravity Probe B ↗Share your answer
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