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At an early age, Arthur B. McDonald was already busy trying to figure out the way things work.

“His mother will tell you that at age five, he used to take apart clocks,” says Dr. McDonald’s wife, Janet. “Very early he was intrigued by how things work.”

It’s that interest in the mechanics of the world that eventually led Dr. McDonald, the 2015 co-winner of the Nobel Prize in Physics, to study the universe on a fundamental level, through physics.

“In high school, I was interested in science, not necessarily physics. And I had a math teacher, Bob Chafe, in Sydney, Nova Scotia, who inspired many to pursue math,” says Dr. McDonald. “When I started studying at Dalhousie, I went to study math and science, but it was other teachers, Professors Ernest Guptill and Innes MacKenzie, who inspired me in physics. I also found that I could do it and it was fun.”

The Nobel Prize win recognizes the immense contributions Dr. McDonald has made over his lengthy career, but particularly honours his longtime research and groundbreaking findings into neutrinos – sub-atomic particles considered the basic building blocks of the universe.

The Sudbury Neutrino Observatory (SNO)

In 1989, he became director of the Sudbury Neutrino Observatory (SNO), located in the Vale (formerly known as INCO) Creighton mine near Sudbury, succeeding Queen’s Professor George Ewan, the Canadian spokesman for SNO the year prior. Working in the world’s deepest underground laboratory, the SNO team – made up of scientists from several Canadian universities – discovered that neutrinos change from one type, or “flavour,” to another on their journey to Earth from the core of the sun. This finding confirmed that these fundamental particles have a finite mass and that the current models for energy generation in the sun are very accurate.

Dr. McDonald shares the prestigious Nobel win with Japanese scientist Takaaki Kajita, a professor at the University of Tokyo who similarly found, at the Super Kamiokande detector in Japan, that neutrinos created in the atmosphere underwent a metamorphosis in their journey to Earth.

“I am truly honoured,” says Dr. McDonald. “While I am a co-winner of the Nobel Prize, the honour really represents a culmination of the hard work and contributions of many colleagues with whom I have collaborated during my career.”

The early years on the east coast

Dr. McDonald grew up in the small Nova Scotia city of Sydney, where a tightknit family gave him a strong sense of community and laid the foundation for his successful career.

“There was a lot of knowledge and respect there, within his family,” says Mrs. McDonald, who is also from Sydney and met Dr. McDonald at a dance in high school. The couple will celebrate their 50th wedding anniversary in 2016.

“He’s very clever, but along with that, he has a really good sense about things. He’s multi-faceted,” she says.

“Art has a wonderful way with people. He is very humble and respectful, and I think that’s why the SNO collaboration has done so well. They are all very collegial. That starts with the director and permeates through the group.”

I am truly honoured. While I am a co-winner of the Nobel Prize, the honour really represents a culmination of the hard work and contributions of many colleagues with whom I have collaborated during my career.

Dr. McDonald left Sydney for Dalhousie University in Halifax, graduating in 1964 with a BSc (Honours) in physics and a year later, with an MSc in the same field. From there, he headed south, and west, to complete a PhD in nuclear physics at the California Institute of Technology in Pasadena. He and Mrs. McDonald came back to Canada in 1969 and settled in Deep River, where Dr. McDonald worked at the Chalk River Nuclear Laboratories with Atomic Energy of Canada, performing fundamental nuclear and particle physics experiments with accelerators and reactors.

From Princeton to ľĹĐăÖ±˛Ą

After 12 years in Deep River, Dr. McDonald was offered a position at Princeton University. They were raising their four children in Deep River, and while somewhat reluctant to leave, the family moved and stayed in Princeton until 1988, when Dr. McDonald came to Queen’s on sabbatical for a year and stayed on permanently – a move encouraged by Dr. Ewan as well as Dr. Don Taylor, head of Physics at the time.

“While I was at Chalk River, I was already working with scientists from Queen’s who became the SNO team here,” says Dr. McDonald. “And when I was at Princeton, I returned to Chalk River in the summers to complete research. Our SNO collaboration began in 1984 and I started to study low radioactivity materials in our labs at Princeton.”

As project director at SNO, now known as SNOLAB, Dr. McDonald was responsible for the development, construction, commissioning and operation of the unique underground site, as well as the analysis and presentation of scientific results. It was his persistence, dedication and leadership over many years that paved the way to the significant scientific breakthroughs made by the team.

“We knew that we could make a significant measurement on the property of neutrinos, if we could only complete this very complex project and control radioactivity to an enormous degree,” he says.

At SNO, Dr. McDonald’s leadership led to the creation of the ultimate in a low-radioactivity instrument using 1,000 tonnes of heavy water as the heart of a solar neutrino detector. Whereas previous experiments had primarily observed electron neutrinos, SNO also observed the total flux of all active solar neutrinos and could show decisively whether the electron neutrinos had changed into other types.

The results from the SNO experiment provided clear evidence that the neutrinos from the core of the sun were changing their type, a process arising from neutrinos of finite mass undergoing oscillations. This result, coupled with results for atmospheric neutrinos from Dr. Kajita’s experiment in Japan, requires modifications to the Standard Model of Elementary Particles to include massive neutrinos. SNO results also provided a very accurate confirmation of current models of the sun and its energy-generation processes.

While Dr. McDonald says he’s retired, he still comes into campus regularly and is busy contributing to two experiments at SNOLAB.

It was a feeling of amazement. I am so grateful, for the award, and for all my colleagues and students who have been alongside me throughout my career.

Of course, the Nobel changes things. It’s a distinction he knows will shift his life in exciting ways. At the same time, he feels a responsibility to represent his colleagues, university and country well when in the spotlight that this prize brings. “It was a feeling of amazement,” says Dr. McDonald. “I am so grateful, for the award, and for all my colleagues and students who have been alongside me throughout my career.”

Breakthrough Prize

Arthur McDonald, representing the Sudbury Neutrino Observatory (SNO) Collaboration, also received the 2016 Breakthrough Prize in Fundamental Physics, which recognizes individuals who have made profound contributions to human knowledge. The partnership received the prize at a ceremony and gala on Nov. 8, 2015 at the NASA Ames Research Centre in Moffett Field, California.

More on Dr. McDonald's research

This article was previously published in the ľĹĐăÖ±˛Ą Alumni Review magazine.