NIST measures gravity with masses small enough to move by hand

For over 225 years, scientists have struggled to pinpoint the value of big G, the universal gravitational constant, despite its fundamental role in governing the cosmos. Now, after a decade-long effort, NIST physicist Stephan Schlamminger has unveiled results from a painstaking measurement of this elusive constant. “The time had come to open the envelope,” Schlamminger admitted, unsure of the secret number his team’s work would reveal. Despite gravity’s constant presence, big G remains the least well-known of the four fundamental forces, a disparity researchers hope to resolve with increasingly precise experiments using masses small enough to move by hand. The NIST team’s replication of the 2007 BIPM experiment employed a torsion balance featuring eight cylindrical metal masses, a design rooted in the landmark 1798 experiment conducted by Henry Cavendish, to refine the measurement of the gravitational constant. This approach demanded extreme precision given the inherent weakness of gravity and the minuscule scale of the forces being measured, forces exerted by masses some 500 billion trillion times smaller than Earth. Researchers meticulously controlled for environmental variables, including temperature and pressure fluctuations, to minimize potential sources of error in the delicate measurement process. To ensure the objectivity of their decade-long undertaking, NIST…