NIST gravity measurement deepens disagreement over fundamental constant

A decade-long NIST experiment measured the universal gravitational constant at 6.67387 × 10-11 meters cubed per kilogram per second squared, 0.0235% below a leading 2007 French measurement using a similar approach. The team used blinded data analysis and tested copper and sapphire masses, which produced essentially the same result. Researchers say unrecognized experimental effects remain the likeliest explanation for the mismatch.