What are you working on?

The main thing I work on at MIT is the theory of elementary particles , which is an attempt to get a mathematical description of the smallest constituents of matter. We’re trying to understand nature at distance scales that are infi nitesimal. Now, a lot of people have trouble understanding why we would want to do that. Interestingly, those same people don’t seem to have much trouble understanding why someone would want to study the sky. If you ask most people if they think it is worthwhile to study the heavens, they say, “Yes. It’s interesting to know what makes stars burn, it’s interesting to know what galaxies are made of, it’s interesting to know what the universe looked like after the big bang, and it’s interesting to know how big the universe is.” Well, elementary particle physics is an investigation of nature, but instead of looking out, we look in. We try to understand things on the smallest scales. And it turns out that when you start to look at things on a very, very tiny scale, you start to see phenomena you never would have anticipated.

How would you describe it more specifically?

We use nature as our blueprint. A leaf is a solar energy machine. It uses light to make oxygen and hydrogen. People don’t know that, but it’s a solid form of hydrogen (NADH) that gets stored with CO 2 to make sugar. So, we try to fi gure out how a leaf works. We do this by capturing its essential ingredients and making compounds that have its basic elements. Our task is to replace the leaf with a substance that can effectively do the same job. That’s called artifi cial photosynthesis. We literally build molecules that can capture light and then act on water to perform this hydrogen and oxygen splitting. After making the compounds bond by bond, we expose them to lasers in order to imitate the effects of the sun. The lasers allow us to turn the light on and off quickly and observe what happens to all that energy. The light produces an excited state. We can then take a series of pictures and follow molecules and energy fl ow. When we see how energy is captured in the excited state, we try to convey it to the water molecule. If we see that things aren’t working well we go back. It’s like being an engineer of molecules . We change the molecules around, we add things, we take things away, and, hopefully, we make a better molecule.

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