Observations of Brownian Motion in Nature

First systematic observations of Brownian motion in nature were made by the French physicist Jean Perrin in 1909. He recorded the position of colloidal particles suspended in a liquid every 30-50 seconds.

The irregular motion of suspended particles in a solution as recorded by Jean Perrin (http://www.mpiwg-berlin.mpg.de/en/research/projects/NWGII_BiggBMcorr - Charlotte Bigg)

Note that in the picture above the straight lines are due to interpolation. Perrin noted that by shortening the observation time the paths became more ragged on even smaller scales. This was the first experimental confirmation of Einstein's theory of Brownian motion, and on diffusion in suspension. The observed Brownian motion occurred in 3D. Can we also observe 1D Brownian motion in nature?

The main problem to observe 1D Brownian motion in nature is the fabrication of structures that which are narrow enough , so that the microscopic diffusion process becomes 1d. This means that the structures need to be of the size of the diffusing particles.

The first branch of science to achieve this goal has been organic chemistry. Starting from around the mid 1960s there has been put a considerable amount of work on low dimensional materials conducting electric current. Reason was the prediction of a theory that superconductivity would be achievable at room temperature in quasi 1D structures. Although this aim has not been achieved, a lot if interesting physics has been discovered on the way. Next week we will discuss the case of 1D Brownian motion in a synthesised 1D organic conductor.