Brownian Motion Simulation

Brownian motion is the irregular movement of a larger particle caused by countless collisions with smaller particles. In this app, the grey circles act like fast-moving air molecules, and the red circle represents a heavier particle drifting through them. When the particles collide, their momentum is exchanged, which makes the red particle wobble, slow down, or change direction.

Use the speed slider to make the grey particles move faster or slower, and use the red mass slider to see how inertia changes the motion of the larger particle. A heavier red particle is harder to push around, while a lighter one responds more strongly. You can also hide the grey particles, trace the red particle’s path, and clear the trail whenever you want to study the motion more closely.