Dr. Ferenc Dalnoki-Veress, scientist-in-residence at the James Martin Center for Nonproliferation Studies (CNS) and an adjunct professor in the Middlebury Institute’s Nonproliferation and Terrorism Studies program, was a member of the Sudbury Neutrino Observatory (SNO) team whose work was recently honored with the 2015 Nobel Prize in Physics.
Led by Dr. Arthur McDonald, the Canadian team built and operated an 18 meter in diameter spherical detector located in a 10 story high cavity two kilometers underground in a nickel mine. As Ferenc says, “sometimes doing physics takes hard work!” He adds that they did all this “to get a better understanding of how the sun works and how the particles called neutrinos fit in with our understanding of cosmology.” The combined work of Arthur McDonald’s team and previous research conducted by Dr. Takaaki Kajita of Japan showing that neutrinos metamorphose and have mass “has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe,” according to The Royal Swedish Academy.
“You might ask why do crazy physicists go deep, deep underground to look at the sun?” says Ferenc, going on to explain that neutrinos go through everything—“to a neutrino, two kilometers of rock is like butter.” Ferenc is known on campus for his ability to “translate” complicated science into terms more easily understood by non-scientists. “Neutrinos are hardly stopped by anything. However, there are so many of them—billions of them passing through your finger nail right now coming from the sun and distant stars—that even though they are not easily stopped, once in a while they will hit the SNO detector and register a signal. A detector on the surface rather than underground would detect millions of cosmic rays that also bombard us and it would be difficult to discern a neutrino from a cosmic ray.”
You could say that measuring neutrinos is a way of looking straight into the center of the sun. “What is special about neutrinos is that not only do they go straight through the earth, they also come straight from where they were produced in the center of the sun, unlike light particles which bounce around and lose all information about how they were actually produced.”
Neutrinos come in three (some say four) flavors, say “vanilla, chocolate, and strawberry,” but in the sun they are only created as “vanilla.” “Our team devised an experiment to measure not only the vanilla flavored neutrinos, but all the other flavors as well. What we found back in 2002 was that neutrinos created as vanilla neutrinos change as they travel through the sun into other flavors. Imagine how shocking it would be if someone sent you vanilla ice cream and it arrived as a combination of vanilla and chocolate ice cream.” In the world of physics this was huge news, for the fact that the neutrinos could change their identity, or “flavor” meant that they had to have some mass. “That was not part of our understanding at the time!”
“The discovery we made was groundbreaking because it confirmed with high precision how the sun generates its energy, and may even help in developing fusion reactors in the future. It also had profound implications for cosmology because neutrinos are the second most prolific particle that we know of. Giving it a finite mass suddenly meant the universe had more mass and cosmologists had to adjust their models to accommodate that fact.” Ferenc says we are still far from using “neutrino beams” to communicate as envisioned in Star Trek. Connecting directly back to his work at CNS, Ferenc adds that neutrinos (actually the anti-neutrino twin of the neutrino) are emitted from nuclear reactors and nuclear explosions. “I can’t help but dream that one day we will definitively detect all clandestine nuclear explosions using an array of neutrino detectors like SNO detectors around the world.”
Dalnoki-Veress holds an MSc and PhD in high energy physics from Carleton University, Canada.