Gravity Probe B

Gravity Probe B was a scientific experiment launched in 2004 to test predictions of Einstein's general relativity. It used ultra-precise gyroscopes—small spinning spheres—to measure two effects caused by Earth's gravity: how the spinning axes shifted over time, indicating "frame-dragging" (the twisting of space-time), and how the axes gradually pointed toward distant stars, reflecting the curvature of space. The findings confirmed Einstein’s predictions with high accuracy, providing strong evidence that gravity affects the fabric of space-time itself, not just a force acting at a distance.