You know the scene, you’re at a gig, maybe even at a festival, and your favourite band comes on. Their opening number is one of your favourites and you head for the mosh pit, risking a black eye or losing your shoe for the sheer enjoyment of it all. You barely need to put any effort in and you get pushed about like a ping pong ball, and the more you push back the harder you seem to fly into the next person.
It feels like you’re at the centre of the universe, this is your moment, but from a distance you bear an uncanny resemblance to a physical phenomenon that is all around us. It’s common knowledge that air is a gas, but have you ever thought about what this means? Invisible gas particles are constantly flying around and hitting into each other, as well as into us. We take this knowledge for granted but this wasn’t always known, so how did we find it out?
A botanist called Robert Brown, musing one day on life and the universe, as you do, noticed that when little pollen particles landed on water they didn’t just float there like something larger might. Instead, they did a crazy little jig, darting this way and that at random. The cause of this is easy to see if you imagine a mosh pit in the dark, with one person wearing a glowing outfit. From the outside it would seem that this person was acting very weirdly, jerking about and constantly moving. But you know this is just what happens when good music comes on.
And so it is with the pollen particle, the water molecules acts much the same as the gas particles in the air, hitting into it at random and pushing it about. Of course, at any given instant this could mean a small movement or a large one in any given direction, leading to the crazy random motion that Brown saw and called, in true egotistical style, Brownian Motion.
This discovery led to investigations of gases and ultimately a much better understanding of the world today!