My Research Part 1: Brownian Motion

NOTE: This post is the first in what will be a series of posts trying to explain what it is that I research.  I will make every effort to make it accessible to the layman (my family) so if you are a physicist you can likely skip the first few posts in the series.

To begin to understand my research, you need to first understand what Brownian motion is. It is really important to physicists and chemists and biologists. Basically any science that deals with stuff about the size to be seen under a microscope will have to deal with Brownian motion.

An easy way to understand Brownian motion is to first picture yourself floating freely in a room with no gravity, just like you were in space.

I only know how to draw in Microsoft Paint, but I hope you get the idea

Then, when you are peacefully floating around, there are hundreds and thousands of super balls that are shot into the room in random directions bouncing all over the place!

This sounds like a lot of fun, but I imagine the novelty would wear off quickly.

It is important to remember that the direction these balls are traveling in is random. Because you are in zero gravity with these balls hitting you at random locations all over your body, they are going to push you a little bit with each collision.  So, if we were to very accurately measure your position in the room, you would not be sitting still, there would be small fluctuations in your position around the spot where you started.  Over a long period of time, you will stay in the same spot you started, because the balls are hitting you from every side of you with the same frequency, but it is these tiny fluctuations in your position that is the important part of this discussion.

Now, let’s unravel the analogy here.  First, instead of a person floating in zero gravity, imagine we are actually dealing with a little plastic bead that is 1 micrometer in diameter (about 1/100 of a human hair) that is suspended in water.  Also, rather than super balls flying around, individual water molecules are zooming around according to the temperature of the solution.  The hotter the solution, the faster the water molecules are moving.  If we look at the bead under a microscope, we would see it jiggling around because the water molecules are hitting it (the water molecules are much too small to see).  This jiggling around is what we call Brownian motion.

You might be thinking, “What’s the big deal, so tiny things don’t sit still, does it matter?”  Yes. It matters so much in fact that describing the mathematics behind Brownian motion is what Albert Einstein won his Nobel Prize for, not relativity as most people think.  It turns out that Brownian motion is of vital importance to facilitate pretty much everything that happens in our cells.  So, without it, life would have never evolved and you would not be sitting at a computer reading this.

Stay tuned for the next installment of My Research.  We will discuss how to use Brownian motion to create liquid crystals through depletion interactions as well as what those words mean!

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