Dark Matter

Moira Gresham
Assistant Professor of Physics

Theoretical particle physicist and cosmologist Moira Gresham, Assistant Professor of Physics, named to NerdScholar’s 40 under 40 list of top professors. But if Moira Gresham’s so smart, what’s the deal with dark matter?

Whitman Magazine: Are you really a nerd?

Moira Gresham: I guess a lot of people would classify me as a nerd in the sense that I’m focused on academic things and I’m not really that up on popular culture. But I don’t really like thinking of myself as a big nerd. Although I guess there was that period in high school when I wore socks and sandals to school.

What makes you not a nerd?

I’m somewhat athletic, and I don’t spend my hours reading a lot of science-fiction and solving Rubik’s Cubes – not that there’s anything wrong with that. I do get outside.

What is dark matter and why should we think about it?

Dark matter is, as the name suggests, dark.

Let me guess. There’s more.

Over the past several decades, we’ve found that there’s a lot of this stuff out in the universe. It’s dark and it’s matter. The matter part is that it interacts through gravitational interaction. It pulls on other matter in the same way as the stuff you and I are made of, gravitationally speaking. There’s a lot of it. It outnumbers the stuff planets and stars are made of by about 5:1, at least locally in the universe.

Ah, that makes perfect sense.

We don’t know what it is but we know it’s there, and our natural human curiosity compels us to investigate its identity. Initially people thought, “Oh, maybe there’s a lot of dust or really dark planets,” but because of the observations that have been made, we are now quite confident it’s actually not made of neutrons and protons like normal matter. It’s not made of electrons. It’s not made of neutrinos or the other sorts of matter particles we’re aware of.

Why is it important?

We have a good model describing the stuff you and I are made of at a really fundamental level. It works phenomenally well in helping us describe materials and make predictions about what happens in our labs, but we know our model is incomplete – one of the most obvious indications of this being that dark matter exists. If we can figure out what dark matter is, we hope it will help us better understand the fundamental laws of physics. It would be one step toward a better understanding of the fundamental constituents of the things we’re made of.

I read that only 15 percent of physics professors in the U.S. are women. Why is that figure so low?

The short answer is, I’m really frustrated by that question, and I ultimately don’t know. It’s uncomfortable to go into an area where you’re conscious you don’t fit in. At least the number of females getting Ph.D.s in physics has been slowly rising.

What challenges did you have on the way to earning your Ph.D.?

In relation to being a female, I faced relatively few challenges in graduate school. My incoming graduate class had an abnormally large percentage of females. Granted, that was six or seven out of 30, but it was enough that I felt reasonably comfortable. The context in which I feel most uncomfortable is at physics conferences. You’re in a room with 200 people and you can only pick out 10 females. It’s clear people at conferences are remembering me as “the female.”

Why are you drawn to physics?

Physics reveals a principled and simple way in which nature works. Take, for example, Newtonian mechanics. The foundation of Newtonian mechanics is three basic statements that are enormously powerful in describing how things move. Then there’s the fact that I really like solving problems. It’s fun. Generally speaking, physics seems to jive with the way I think about things.

— Edward Weinman