For over two centuries, determining the exact value of the universal gravitational constant, known as big G, has challenged scientists.Stephan Schlamminger and his team at the National Institute of Standards and Technology (NIST) spent nearly a decade conducting an ultra-precise experiment to measure this fundamental constant.To prevent bias, a crucial number in their data was kept hidden in a sealed envelope, only revealed once the experiment was complete.

When Schlamminger finally opened the envelope in 2024, the result was both reassuring and disappointing: while it broadly aligned with expectations, it did not exactly match a previous French experiment.Their measured value, 6.67387×10^-11 m^3/kg/s^2, was 0.0235% lower than the French measurement.

Although this small difference has no practical impact on everyday life, it is significant to physicists, who usually see fundamental constants agree to far more precise levels.

The NIST team used advanced torsion balance techniques, a modern version of Henry Cavendish's 1798 experiment, and tested both copper and sapphire masses, ruling out material effects as the source of discrepancy.

Schlamminger emphasizes that precise measurement is key to understanding the universe, even if it challenges expectations, and he hopes future generations will continue investigating the mysteries of gravity.