Brownian motion

The term Brownian motion (in honor of the botanist Robert Brown) refers to either

History

Jan Ingenhousz made some observations of the irregular motion of carbon dust on alcohol in 1765 but Brownian motion is generally regarded as having been discovered by the biologist Robert Brown in 1827. The story goes that Brown was studying pollen particles floating in water under the microscope. He then observed minute particles within vacuoles in the pollen grains executing the jittery motion that now bears his name. By doing the same with particles of dust, he was able to rule out that the motion was due to pollen being "alive", but it remained to explain the origin of the motion. The first to give a theory of Brownian motion was Louis Bachelier in 1900 in his PhD thesis "The theory of speculation".

Related Topics:
Jan Ingenhousz - Carbon - Dust - Alcohol - 1765 - Robert Brown - Louis Bachelier

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

At that time the atomic nature of matter was still a controversial idea. Albert Einstein and Marian Smoluchowski observed that, if the kinetic theory of fluids was right, then the molecules of water would move at random and so a small particle would receive a random number of impacts of random strength and from random directions in any short period of time. This random bombardment by the molecules of the fluid would cause a sufficiently small particle to move in exactly the way described by Brown. Theodor Svedberg made important demonstrations of Brownian motion in colloids and Felix Ehrenhaft, of particles of silver in air. Jean Perrin carried out experiments to test the new mathematical models, and his published results finally put an end to the century-long dispute about the reality of atoms and molecules.

Related Topics:
Albert Einstein - Marian Smoluchowski - Kinetic theory - Theodor Svedberg - Colloid - Felix Ehrenhaft - Silver - Air - Jean Perrin - Atom - Molecules

~ ~ ~ ~ ~ ~ ~ ~ ~ ~