Brownian motion was one of the many things explained by Einstein. It's the seemingly random 'jiggling' of particles caused by atoms hitting them. Under some circumstances, though, it's not so random. Find out about the strange patterns of Brownian motion, and how physicists have observed them for the first time.

Back in 1827, Robert Brown was observing pollen grains in water under a microscope. He was having a difficult time, since the little suckers kept jumping. Each grain moved in a random direction at a random time, not flowing all in one direction the way they would if a larger outside force was acting on them. Brown wrote about the tiny, random movements, and lucked out. Despite the fact that the phenomenon had been observed in one medium or another since ancient Greece, he ended up being the namesake of the motion. Although people came up with the correct explanation for it â€” the grains were taking constant hits from atoms and molecules too small to be seen â€” Einstein finally came up with a way to establish a way to measure how the grain moved.

Although he didn't follow the path of the individual movements of the grain, he showed that the grain took 'The Drunkard's Walk.' The Drunkard's Walk compares the random movement of molecules to the random movement of a drunk. This particular drunk is asked to walk ten steps from his original position. But he's so blotto that every step is in a random direction. The first step might be to one side, the next back to where he started, the next to the other side, and so forth. To take ten steps in a line is a task that spans length, and length is one dimension, so we only deal with one value. When the steps can be taken in any direction, the task turns from one that spans length to one that spans area. Area is two dimensions. To find an area, we multiply length times width. So if we want the drunkard to go ten steps from his starting point, we calculate that he will take ten times ten, or a hundred steps to do it. This is a sign of true random motion in two dimensions - the distance gone is the square root of the number of steps it takes to get there.

The motions of the molecules were too quick to count steps, but Einstein showed that, over any amount of time they moved from their starting points in the manner of The Drunkard's Walk. Give a single pollen granule one minute, and it will move a single unit of distance from its starting point. Give it four minutes and it will move two units from its starting point. Give it nine minutes and it will move three units. This same works if the unit of time is hours or days - though the pollen would require a large slide and would be a pain to watch. The distance it covers will always be proportionate to the square root of the time it's given. Brownian motion is a true Drunkard's Walk. It's motion in a random direction.