Three Minute Thesis

I'm in the ANU finals for the three minute thesis competition. I thought I'd post the text here:



The most wonderful aspect of science is it can take parts of the world that on the surface of it appear mundane even boring, and reveal layers of intricate detail and mysteries of profound importance.

A great example of this, is the most common substance on the surface of the earth: Salt water. This seemingly mundane substance is actually quite mysterious and literally vital for life.

When you take salt and dissolve it in water it breaks apart into ions such as sodium and chloride. These are called ions because they carry electrical charge, just like a balloon that’s been rubbed against the carpet. Because they are charged they can carry electricity, and can therefore be for our body what electrons are for a computer or electric motor.

It's the flow of ions in and out of your cells that causes your muscles to flex and carries the electrical signals in your brain that make up consciousness.

Because these ions are so important the body has developed a complex array of machines called proteins, in order to move these ions around. These proteins are a lot like the different parts of a pinball machine, bouncing and directing the ion. If we wanted to know how to fix a broken pinball machine we need to know what each of the parts does to the ball. In the same way, we want to know whether a protein will bounce an ion away or pulls it towards it. The number of potential applications of this knowledge is vast ranging from drug discovery to water treatment.

Our simple, classical theories of these ions say that they should behave according to their charge. This means that if we take simple table salt, sodium chloride, and its two closest relatives: Lithium chloride and potassium chloride. These three different salts should all behave identically. But don't at all. In fact lithium chloride is somehow an effective treatment for depression. This used to be an ingredient in 7up by the way hence the up as well as their slogan, taking the ouch out of grouch. At the other extreme is potassium chloride a component used in the lethal injection.

Now proteins are very big and complex. So we want to start with a much simpler but very closely related problem: If an ion is near another ion or near the air-water surface is it pushed away or pulled towards it and how strongly? To answer this question I have built what we call a mathematical model.

This just means that I have made some assumptions and written these down using symbols and equations. This is just like writing down the beginning of a story  But instead of just making up the ending to the story, we use the laws of mathematics to calculate the ending. To then tell if this story is true or just a fiction we compare the calculated ending with real experimental measurements.

In my case I compare with the amount of energy it takes to remove salt from water, and how the strength of the air-water surface changes as we add salt to it. Because the model does a good job I can say that this vital substance is no longer quite so mysterious.