Brownian motion
Evidence for the movement of particles in liquids came to light in 1827 when a botanist, Robert Brown, observed that fine pollen grains on the surface of water were not stationary. Through his microscope he noticed that the grains were moving about in a random way. It was 96 years later, in 1923, that another scientist called Norbert Wiener explained what Brown had observed. He said that the pollen grains were moving because the much smaller and faster-moving water particles were
constantly colliding with them. This random motion of visible particles (pollen grains) caused by much smaller, invisible ones (water particles) is called Brownian motion, after the scientist who first observed this phenomenon. It was used as evidence for the kinetic particle model of matter.
