What is the Cavendish balance and how does it work?

The Cavendish balance, invented by Henry Cavendish in 1798, is an apparatus designed to measure the force of gravitational attraction between masses. It consists of a horizontal bar suspended from a thin wire, with small lead balls attached to each end. When larger lead spheres are brought near the smaller ones, the gravitational pull causes the bar to twist, and the angle of this twist is measured using a scale. This allows for the calculation of the gravitational constant and ultimately leads to the determination of the Earth's density.