ABSTRACT
Under equilibrium conditions, the dynamics of a dilute concentration of particles of microscopic dimensions immersed in a liquid at a temperature T are random, and if the average velocity of a particle is measured over a sufficiently long time interval, for example in the x-direction, it would be zero,
= 0. This is a consequence of the fact that the particle can move in any direction with equal probability. Whereas the average velocity is zero, the velocity of the particle at a given instant is typically not zero because fluctuations of the velocity occur and are specified by . These fluctuations increase with temperature, and more massive objects experience smaller fluctuations. The random, statistically fluctuating, and incessant motions of the particles in the liquid typify the phenomenon of Brownian motion.
