Brownian motion

This phenomenon consists in the completely disordered movement of small particles, but much larger than atoms or molecules, visible under a microscope, which float on the surface of a liquid or are suspended in a gas: pollen grains, dust, fine powder. Unlike thermal agitation, this phenomenon is observable, at least under a microscope. Like thermal agitation, Brownian motion intensifies with increasing temperature.

Explanation of the phenomenon: small particles are hit by a large number of microparticles (atoms, molecules) that are in full thermal agitation, so they are also set in motion, but at much lower speeds.