Scientists Crack Sealed Envelope After 10 Years, Gravity Still Defies Precise Measurement
NIST physicist Stephan Schlamminger spent a decade measuring the universal gravitational constant while keeping his own results hidden from himself.
After nearly a decade of painstaking experiments, physicist Stephan Schlamminger finally opened a sealed envelope containing a secret number that would reveal whether his team had successfully measured one of physics' most elusive constants. The dramatic moment marked the culmination of years spent trying to pin down the exact strength of gravity, a challenge that has frustrated scientists for more than 200 years despite its fundamental importance to understanding the universe.
Schlamminger and his colleagues at the National Institute of Standards and Technology (NIST) had spent the better part of 10 years recreating a landmark 2007 experiment performed by the International Bureau of Weights and Measures in France. Their goal was to measure "big G," the universal gravitational constant that governs everything from falling apples to the motion of galaxies, with extraordinary precision.
The challenge of measuring gravity's strength stems from its surprising weakness compared to other fundamental forces. While electromagnetic forces can easily lift a paper clip against Earth's entire gravitational field using just a small magnet, detecting gravitational attraction between laboratory-scale objects requires incredibly sensitive equipment. The masses used in such experiments are roughly 500 billion trillion times smaller than Earth, making the gravitational forces between them extremely difficult to measure accurately.
To avoid unconscious bias that might influence his analysis, Schlamminger had asked colleague Patrick Abbott to secretly subtract a hidden value from some of the experimental data. Only Abbott knew this number, and until the envelope was opened, Schlamminger had no way of determining his experiment's true result. The envelope had nearly been opened once before in 2022, but Schlamminger stopped at the last moment after reading additional research.
Despite more than 225 years of increasingly sophisticated experiments since Isaac Newton first described gravity mathematically, modern measurements still produce slightly different answers for big G. The differences are tiny—about one part in 10,000—but they exceed expected experimental uncertainties, raising uncomfortable questions about whether scientists are missing subtle experimental flaws or whether there are gaps in our understanding of gravity itself.
