The Discovery of Brownian Motion

In 1829, the Scottish botanist Robert Brown observed microscopic grains of pollen suspended in water. Instead of moving in straight lines or staying still, they moved about in an erratic and entirely unpredictable manner. They followed, as it were, a ‘drunkard’s path’:

To Brown, the pollen grains seemed invested with the primordial rudiments of life which gave imbued them with the capacity to meander about like drunkards following a random walk. Cool! Too bad though: he was wrong. But like so many things, even though his hypothesis was incorrect, the search for the correct explanation changed the way we look at the world. The correct explanation for Brownian motion is that the grains of pollen were being bombarded by myriads of water molecules moving at random. The molecules were too small to be resolved by the microscopes. Their presence could only be inferred by observing Brownian motion.

So, Brownian motion is the name given to the random motion of particles in gases or liquids. The particles follow a ‘random walk’ or a ‘drunkard’s path’ because they are round and elastic, bouncing off one another in proportion to the temperature of the system. Or so the kinetic theory of gases would argue. If this seems self-evident, it sure wasn’t in 1829. Molecules: what are those? Didn’t matter contain phlogiston, an element with the property of fire which enables combustion? And so on. It wasn’t until 1905 that someone figured out the true cause behind the disturbingly random movements in Brownian motion. It took Einstein to figure it out.

Levels of Uncertainty and Order in Brownian Motion

Now, what is most interesting about Brownian motion is that here is a system that is completely random, unpredictable, and lacking certainty on one level but exhibits form, predictability, and order on another level.

On a micro level, the random walk of a gas particle in a container is, well, completely random. That is to say, there is no force in the universe which is capable of predicting whither it will go. God doesn’t know. Ask Laplace’s demon and he would tell you many other things, but the random walk is beyond his intelligence.

All this uncertainty: very frustrating! What can be done? Well, nothing can be done. The uncertainty resolves itself! How? On a macro level, a container of gas exhibits form, predictability, and order. Gas in a container-that is to say millions of billions of particles all randomly walking-is governed by such things as Boyle’s Law (pressure inversely proportional to volume) and the transfer of kinetic energy (temperature) of the container to the outside world is also well regulated.

How it happens that on a micro level things are completely random (individual particles of gas randomly walking) and on a macro level things are completely determinate (billions of particle of gas have well defined characteristics including temperature, energy, pressure, etc.,) is beyond me. At some point, however, chaos gives way to order. Keep this in mind for now.

Tragedy, Comedy, and History

Ever thought about how randomness, unpredictability, and the unexpected dominate comedy and tragedy. In comedy, the unlikely couple overcome cantankerous patriarchs, and social and economic barriers to become happily married. In tragedy, the unexpected also dominates: Birnam Wood comes to high Dunsinane hill every time. But now turn your attention to history. Patterns emerge. Some of the patterns are linear. Fukuyama thought that history aimed towards achieving democratic capitalist societies. Then history ends. Marx thought history strives towards the communist revolution. Patterns can be linear. Polybius believed in anacyclosis, the doctrine that constitutions move cyclically from monarchy to tyranny to aristocracy to oligarchy to democracy to ochlocracy and then back again to monarchy. The patterns in history are reflective of a reality that has form, order, and is predictable. If tragedy, comedy, and history all represent reality, is comedy and tragedy correct or is history correct? After all, the unexpected reigns in comedy and tragedy while the expected reigns in history.

Come back now to the behavior of gases on a micro and macro level. On a micro level, Brownian motion is the term used to describe the unexpected ways particles move around at random. On a macro level, patterns emerge that are predictable (e.g. as pressure increases volume decreases). Tragedy and comedy look at the world from a micro level. They usually dramatize the actions of a day or less (the unity of time). History looks at the world from a macro level. It records actions taken place over decades and centuries. In this way, the short term randomness of a day yields to long term order and patterns. So comedy and tragedy versus history is like looking at Brownian motion: on a small scale, disorder. On a large scale, order. Neither are right or wrong. They are looking at the same reality from a different perspective.

It always astounds me how many parallels there are between science and art. It may have something to do with how we look at the world. Whether we are artists or scientists, we look at the world with the same set of eyes and the same intellectual apparatus. So perhaps the parallels between science and art rests on humanity and the all-too-human way of understanding things.

Until next time, I’m Edwin Wong and I’m Doing Melpomene’s Work by figuring out the secrets to tragic literary theory.