For more than 200 years, scientists have struggled to pin down the exact strength of gravity — and one physicist spent a decade chasing the answer while keeping his own results hidden from himself. Stephan Schlamminger and his team at NIST painstakingly recreated a landmark French experiment designed to measure “big G,” the universal gravitational constant that governs everything from falling apples to galaxies. When he finally opened a sealed envelope containing the secret number needed to decode the experiment, the results brought both relief and disappointment