Scientists have reported a new measurement of the universal gravitational constant, known as "big G," which differs slightly from a previous leading result. This has reignited a long-standing puzzle in physics that has persisted for over two centuries. The discrepancy, though small, has raised questions about whether it stems from hidden experimental errors or could hint at a deeper, unknown aspect of physics. The new result, obtained by a team at the National Institute of Standards and Technology (NIST) after a decade of research, was revealed in a sealed envelope. The team aimed to replicate a highly precise experiment conducted by the International Bureau of Weights and Measures (BIPM) in 2007. To avoid bias, physicist Stephan Schlamminger had his colleague Patrick Abbott blind the experiment by altering part of the data. The correction needed to recover the real answer was sealed inside an envelope. Schlamminger delayed opening it in 2022 due to concerns about air pressure effects and finally revealed the result in 2024. The NIST measurement of G was 6.67387 × 10⁻¹¹ meters³/(kilogram·second²), which is 0.0235% lower than the value obtained in the French experiment. This small but significant difference adds to the growing list of conflicting measurements of big G, which has been a point of debate among physicists for years. Both the BIPM and NIST experiments used a torsion balance, an instrument that measures extremely small forces by observing how much a thin suspended fiber twists. This method dates back to a famous experiment performed by English physicist Henry Cavendish in 1798, which was the first to measure the gravitational constant. In both experiments, eight cylindrical metal masses were used. Four larger cylinders were positioned on a rotating carousel, while four smaller masses were placed inside the carousel on a disk suspended from a copper-beryllium ribbon. Gravity between the outer and inner masses caused the torsion balance to rotate, twisting the thin metal ribbon. Researchers also used electrodes beside the inner masses to apply an electrical voltage, creating an electrostatic force that balanced the gravitational torque. Schlamminger's team introduced an additional test using copper and sapphire masses, finding essentially the same result with both materials. The NIST experiment has become another important data point in the ongoing effort to determine the true value of big G. Schlamminger emphasized the importance of every measurement, stating that he is ready to pass the challenge to younger generations of scientists who may one day solve the mystery of the gravitational constant.