Decade-long experiment leaves the strength of gravity unresolved

A decade-long experiment at the U.S. National Institute of Standards and Technology produced a measurement of gravity's fundamental strength that still disagrees with a leading French result. The difference is just 0.0235%, but it is larger than expected from the experiments' stated uncertainty. The researchers measured the tiny gravitational attraction between laboratory masses, concealing part of the data during analysis to reduce bias. Repeating the experiment with copper and sapphire masses gave essentially the same answer. The result, published in Metrologia, leaves the universal gravitational constant less precisely known than other fundamental constants. The researchers consider an overlooked experimental effect more likely than a change to the understanding of gravity.