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Brownian Motion
Brownian motion is the chaotic motion of small particles in a liquid or in a gas, discovered by English botanist Brown. Brownian motion is caused by the collisions of molecules. The amount of these collisions is directly related to temperature.

The velocity of a Brownian particle randomly changes in magnitude and direction, and a Brownian particle's trajectory is a complicated zigzag curve.

Albert Einstein is credited for creating the kinetic theory of Brownian motion. The main implication of this theory is the fact that the square of the displacement < r2 > of a Brownian particle from its initial state, averaged over many Brownian particles, changes in direct proportion with time (in accordance with the law of diffusion).

< r2 > = Dt,
where D is the diffusion coefficient and is proportional to the absolute temperature T.

This model illustrates the chaotic motion of Brownian particles. The computer determines the coordinate of a given Brownian particle over equal intervals of time, and calculates the square of its displacement from the state of equilibrium, averaged over the previous calculations of its coordinates. After 100 of such steps, the computer automatically switches to another particle. The computer also switches to another particle if you press "Reset".

© OpenTeach Software, 2007