Physics

Centuries on, Newton’s gravitational constant still can’t be pinned down

Different labs’ measurements of the strength of gravity don’t agree

An illustration of a hand dropping a weight with a blue sky background.

Big G, known formally as Newton’s gravitational constant, describes the strength of gravity. But its precise value remains a mystery.

Neil Webb

By James R. Riordon

There was a secret inside the envelope in the hands of Stephan Schlamminger, one of the world’s leading experts in experimental tests of gravity. He appeared to be on the verge of opening the envelope during a presentation at the April 2022 meeting of the American Physical Society, to read a number that would reveal whether his latest efforts in a lifelong passion had been a success.