Brownian motion
![This is a simulation of the Brownian motion of a big particle (dust particle) that collides with a large set of smaller particles (molecules of a gas) which move with different velocities in different random directions.](/Images/godic/202502/01/Brownian_motion_large3433.gif")
![This is a simulation of the Brownian motion of 5 particles (yellow) that collide with a large set of 800 particles. The yellow particles leave 5 blue trails of random motion and one of them has a red velocity vector.](/Images/godic/202502/01/Brownianmotion5particles150frame3433.gif")
![](/Images/godic/202502/01/Translational_motion3433.gif"){kind=spacer}
![Three different views of Brownian motion, with 32 steps, 256 steps, and 2048 steps denoted by progressively lighter colors](/Images/godic/202502/01/Brownian_hierarchical.svg3433.png")
Brownian motion or pedesis (from Ancient Greek: πήδησις /pέːdεːsis/ "leaping") is the random motion of particles suspended in a fluid (a liquid or a gas) resulting from their collision with the quick atoms or molecules in the gas or liquid. Wiener Process refers to the mathematical model used to describe such Brownian Motion, which is often called a particle theory.