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Cavendish Torsion Balance (2D) — Measuring Newton's G

A top-down 2D recreation of Henry Cavendish's 1798 torsion-balance experiment: two small spheres on a suspended arm are pulled by large lead spheres, twisting a fiber against its own restoring torque. Drag to pan, scroll to zoom, and read the equilibrium angle off an amplified optical-lever spot to back out the gravitational constant G.

Physics & Mechanics2DModerate60 FPS📱 Mobile-adapted⇄ 3D version

In 1798 Henry Cavendish used a torsion balance to make the first laboratory measurement of the gravitational constant — effectively "weighing the Earth." This top-down 2D companion to the 3D simulation rebuilds the same apparatus and the same physics: a suspended dumbbell of two small lead spheres is drawn toward two large lead spheres placed at opposite corners, twisting the fiber until its restoring torque balances gravity's pull. Adjust the large-sphere mass and fiber stiffness, watch the amplified optical-lever spot sweep across the scale, and read a live estimate of G computed straight from the equilibrium twist angle. Drag to pan the view and scroll to zoom in on the apparatus.

⚙ Under the hood

A top-down 2D recreation of Cavendish's 1798 torsion-balance experiment: two small spheres on a suspended arm are pulled by large lead spheres, twisting a fiber against its own restoring torque. Drag to pan, scroll to zoom, and read the equilibrium twist to back out the gravitational constant G.

gravitytorsion-balancecavendishphysics-historynewtonian-gravity2dmeasurement

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install