Big Things in Small Packages

By Beth Wittbrodt
Big Things in Small Packages
Professor Chris White’s neutrino research could help unlock secrets of universal proportions
Photo by Chris Kirzeder

You don’t need to be a physicist to be engaged by Chris White. Perhaps that’s because White is able to explain the most complex of scientific concepts in the simplest of terms and to turn physics into something that is not only accessible to lay people but exciting to them.

So how does White define physics? “Physicists take the world and explain it using mathematics,” he says. “We study the most fundamental constituents of matter. There’s the protons, the neutrons, the electrons, and the photons. And those four particles are all that’s required to explain the world. So everything from DNA to panda bears to modern buildings can be broken down into these four things. It’s nature at its most fundamental.”

The birth of a new particle

White’s research focus is on the neutrino, or ‘little neutral one,’ one of the smallest particles of matter. Scientists are currently hypothesizing that the neutrino is responsible for everything from the evolution of the galaxy to continental drift. But the neutrino wasn’t always so popular.

The concept of the neutrino was first proposed in the early 1900s by theoretical physicist Wolfgang Pauli to explain the mysterious disappearance of energy that was observed when a neutron falls apart into a proton and electron.

Pauli theorized that a new particle was created with this energy, but he was so ashamed of his unproven idea, he bowed out of the conference at which he should have introduced the neutrino to the public. (He said that he had to attend a town dance and therefore couldn’t make it.) So the neutrino remained unsung until the 1950s, when solid proof of its existence was discovered via a nuclear reactor.

Still, neutrinos didn’t seem all that interesting at first. Scientists thought they were massless and didn’t interact with other particles. (It turns out that particles of matter communicate with each other all the time, kind of like the way we speak through soundwaves.) “There are certain ways that particles can talk to each other to say, ‘Hey, I’m here,’” says White. For example, photons communicate via electromagnetic attraction, and quarks via what physicists call the 'strong interaction,' which is what keeps the protons and neutrons in the nucleus of an atom bonded together. The photons are the social butterflies of the universe—those at the core of the sun have to walk their way out to the surface a few centimeters at a time, and it takes them thousands of years because they keep running into something they want to talk to.

Not so the neutrino. According to White, “The neutrinos that are created at the center of the sun and bang, they’re gone. If you could make something as dense as the Earth and line it up the entire length of the solar system, the neutrino would pass right through it. It simply does not interact with other particles of matter. That’s why the neutrino has been described as the loner of the elementary particles.

So why should we care about little particles that don’t play well with others and are massless? “Because the neutrino makes the short list of fundamental particles of which our entire universe is composed, so it’s worthwhile to figure out the rules by which it works,” responds White. “If you understand the fundamental building blocks, then you should be able to work your way up and understand how everything else works.”

And it turns out we may not know as much about the neutrino as we thought. For starters, it may have mass after all. Every time scientists tried to measure neutrinos, they ended up with far fewer of them than they had anticipated. Where did all those missing neutrinos go? The answer is in their flavor. It turns out that neutrinos seem to oscillate, which means they can essentially change their identity. Neutrinos come in three flavors: electron, muon, and tau. An electron neutrino, though it may be born an electron neutrino, can decide one day it wants to be a muon or a tau neutrino. And according to the laws of quantum mechanics, only particles that have mass can shift from one state to another like this.

“Now, this may not sound all that crazy,” says White. “But to give you a sense of how radical it is within particle physics, it would be equivalent to humans saying they’re going to change their gender overnight. Yes, some do, but they generally need a little more help. And that’s the best part of being a scientist, when all of a sudden something that you had no idea was there is found. And that’s what’s happening right now with neutrino physics.”

Capturing the elusive neutrino

Big Things in Small Packages
Chris White at the assembly of the MINOS Near Detector at Fermilab
Credit Fermilab
Photo by Chris Kirzeder

White is among a group of physicists who are redefining the way we think about the neutrino. He is currently a member of the Main Injector Neutrino Oscillation Search (MINOS) project at Fermilab, a high-energy physics research center in Illinois. The project, which got off the ground earlier this year, involves shooting a beam of neutrinos from Fermilab toward an abandoned iron mine in northern Minnesota, where a giant detector is installed a half mile beneath the earth. Why Minnesota? It turns out that in order for neutrinos to oscillate, to morph from one flavor to another, they need to travel a particular distance, which is approximately that from Chicago to Minnesota.

On its way to Minnesota, the neutrino beam has to go under the Earth’s surface due to its curvature (as well as under a few thousand people, but don’t worry about them—every cubic yard surrounding us already contains trillions of the little guys). Going underground also avoids most of the radiation coming into the earth from space, which might cause interactions unrelated to the experiment.

Since neutrinos are loners, only a tiny fraction of the neutrinos will actually interact in the MINOS detector. The vast majority—more than 99.99 percent—of all the neutrinos created at Fermilab just shoot off into space. “We’re producing trillions of neutrinos every two to three seconds. Our hope is that, each day, one will stop in Minnesota and say hi to us,” says White. “We’re actually looking for the disappearance of muon neutrinos and the appearance of electron neutrinos, so we count how many muon neutrinos we send, and then how many we see at the other end.”

In reality, they’re not actually observing the neutrinos themselves at all, but the products of their interactions with other particles. The different types of neutrinos leave behind different products marking their interactions—an electron neutrino leaves behind an electron, a tau neutrino leaves behind a tau, you get the idea. Depending on funding, the project will continue for at least five years.

The type of basic science in which White and his colleagues engage may not have immediate consequences for our daily lives, but its potential to help reveal clues about the nature of the universe is invaluable.

“As a society, we have decided that an understanding of the world in which we live is critical, not necessarily because it’s going to give us better televisions—though eventually down the line it probably will—but because we feel some things have intrinsic value, such as art and knowledge. I like to put this in that category.”

Chris White: Up Close

Chris White is an associate professor of Physics and has worked at IIT since 1995. He’s taught everything from general physics to upper level courses such as Subatomic Physics, Astrophysics, and Electronics. An electronics lab manual he coauthored with fellow professor Dan Kaplan is even used in physics classes at IIT. In 2003, White received the Excellence in Teaching award, which is given to just one faculty member each year based on peer and student recommendations. He’s also Einstein, or rather, he has dressed up as Einstein for both The Field Museum and Fermilab as part of his numerous ‘physics outreach>’ functions. White actively involves his IIT students in physics demonstrations that educate the public, and he visits area high schools and his local grade school to discuss science with students.

Although he grew up interested in astronomy, White became attracted to particle physics in high school and has been fascinated by it ever since. White notes the connection between the two fields: “The thing that’s so interesting is that there’s this connection of the study of the smallest with the study of the largest, which is cosmology. The smallest are these individual pieces, and the largest is the universe, and the understanding of the universe as a whole is critically dependent on our understanding of what’s happening at the smallest scales.”