How do scientists measure the gravitational constant G?

The gravitational constant G is measured in laboratories using carefully designed experiments that detect the tiny force between masses. The classic method is the Cavendish experiment, first performed in 1797–1798 by Henry Cavendish, which used a torsion balance to measure the weak attraction between lead spheres. Modern versions use laser readouts, vacuum chambers, and vibration isolation, but G remains difficult to determine precisely because gravity is so weak. Its accepted value is about 6.674 × 10^-11 N·m²/kg², but measuring it accurately is still one of the tougher tasks in metrology. The challenge is not knowing how gravity works, but measuring it well in the laboratory.