Arthur McDonald, tall, bespectacled and silver-haired, is hiking down the rocky tunnel of a nickel mine outside Sudbury, Ont., after descending more than two kilometres underground in a mine cage. The space is lit mainly by the roving headlamps worn by his small group. Roof bolts and steel screens brace the rock overhead. The terrain is uneven, and it’s easy to stumble. McDonald, 72, takes slow, considered steps, occasionally turning to warn the others of a treacherous puddle or ditch. Fatigue is a common side effect of time spent this deep underground, where the air pressure is much higher than above ground, but he doesn’t seem to feel it. After walking nearly two kilometres, the corridor widens. Here is the entrance to SNOLAB, the world’s deepest clean underground laboratory, where scientists are busy probing the most profound mysteries of the universe.
As a clean lab, the tiniest speck of rock dust, which is naturally radioactive, is forbidden: It could confuse SNOLAB’s ultrasensitive particle detectors. (These detectors benefit from their location deep underground, where layers of rock and earth shield them from cosmic rays.) Before entering, McDonald and his companions, who include Erica Caden, a young particle physicist from Philadelphia, must first give their steel-toed boots a pressure-washing to blast off mud. Men and women split off into change rooms, strip their mining gear, shower (a soapy scrubbing is mandatory), and don a new wardrobe: lint-free coveralls, goggles and a hairnet. Everyone emerges pink-faced from shower steam into a space that is white, spotless and gleaming—“cleaner than a hospital operating room,” McDonald declares—and a dizzying contrast to the nickel mine outside, one of the dirtiest places imaginable.
There’s something in the superfiltered air at SNOLAB, a sense of anticipation, of validation, as people step forward to greet McDonald. For work performed here, the physicist from Nova Scotia, won a Nobel prize. McDonald led an experiment called the Sudbury Neutrino Observatory (fittingly called SNO for short). In 2002, after years of collecting data, his team demonstrated that bizarre subatomic particles called neutrinos switch from one “flavour,” as physicists call it, to another—there are three types of neutrino—and that they have mass. Neutrinos are called “ghost particles” because they’re so notoriously impossible to catch: Trillions of neutrinos flow through our bodies and right through the Earth every second, as effortlessly as a sunbeam streaming through a windowpane. These “astronomical messengers,” as McDonald calls them, can tell us about the far reaches of the universe, the explosions of distant stars, even the inner workings of our own sun.
The discovery, it’s no exaggeration to say, has reshaped the way we understand our universe. The story of SNO is one of an eclectic group of particle physicists, engineers, miners and Sudbury locals, who came together on the biggest, most ambitious and unlikeliest science project Canada has seen—a particle detector the size of a 10-storey building, buried two kilometres underground—and, against all odds, they pulled it off.
On Oct. 6, 2015, McDonald (known as “Art” to almost everyone) was named winner of the Nobel, along with Takaaki Kajita, who had worked on a separate neutrino experiment in Japan. The winning streak continued. One month later, on Nov. 8, he accepted the $3-million Breakthrough Prize in fundamental physics, awarded jointly to five experiments investigating neutrino oscillation, on behalf of his team. These awards have “lit a fire” under everyone at SNOLAB, says Caden, a postdoctoral fellow at Laurentian University. McDonald will receive the Nobel in Stockholm on Dec. 10, joining the ranks of past winners who include Albert Einstein, Pierre and Marie Curie, and Richard Feynman. He’s among the few Canadians, such as acclaimed short story writer Alice Munro, or Frederick Banting, who discovered the life-saving drug insulin, who’ve received a Nobel. It’s also a first for Queen’s University, in Kingston, Ont., where McDonald is a professor emeritus. “Art was the driving force behind the collaboration,’ says SNOLAB director Nigel Smith. “It was his responsibility to deliver the science. His contribution touched everything.”
McDonald is acutely aware that he didn’t do the work alone. The SNO project was started by 16 people, in 1984; the sum total of authors on its scientific papers, he says, is 274. For historical reasons, the Nobel prize in physics is awarded to a maximum of three people; this year, only two. “What I’m trying to figure out now is: How do I bring 273 people with me [to Stockholm]?” he says.
He just can’t. So, from the day the Nobel was announced, McDonald—described by those who know him not just as a brilliant scientist, but as a team builder who prioritized consensus, a feat sometimes likened to “herding cats,” as fellow physicist David Sinclair puts it—has set out to share the acclaim. He’s been visiting universities that played a role (institutional collaborators include Queen’s, Carleton, Laurentian, Guelph, Princeton and Oxford), skyping in to celebrations when he couldn’t be there, and stirring up local publicity however he can. “When someone says congratulations, my standard response is, ‘Thank you, on behalf of a lot of people,’ ” he says, “which is really true.”
This October day at SNOLAB, McDonald sits in the cafeteria and munches on a bag of SunChips. (Like everything else brought down from the surface, the bag of chips had to be sealed in plastic above ground, then unpacked and cleaned before entering the lab.) Asked if he thinks the awards have lit a fire at SNOLAB, he waves his hand. “In point of fact, people were like that before,” he says. He tells the story of a cleaner who’d leave personalized notes tucked in scientists’ boots outside the lab if they hadn’t been sprayed down well enough. That job is as crucial as any other, he emphasizes: Without perfect cleanliness, the experiments won’t work. McDonald turns to a woman at another table, dressed like him, in blue coveralls. “Brenda,” he calls, “who used to put notes in the boots?” “They still do that,” the woman nods. “You mean you,” McDonald grins. Here is the person responsible for washing his boots, and he’s eager to share credit where it’s due.
“So this is the person who keeps us on our toes,” McDonald says. “Meet Brenda.”
McDonald was born in another mining town, Sydney, N.S., in 1943. His father, Bruce, left shortly afterward to fight in the war. “They needed officers sorely, so he said, ‘Wherever I’m needed, I’ll go,’ ” recalls McDonald’s 93-year-old mother, Valerie. Until Bruce came home, in 1946, Art lived with his mother and two aunts, with his grandparents close by. “That’s where you first learned about communication, humility and respect,” McDonald’s wife, Janet, said to him one recent afternoon, as they sat in his sunlit office on the Queen’s campus.
As a boy, McDonald liked to disassemble clocks. “He’s the type who had a lot of friends,” says his mother, “and the type who didn’t study all that much, because he paid attention in class.” After the war, McDonald’s sister, Faith, was born, 10 years his junior. (She’s a retired social worker in Dartmouth.) Their parents were active in the community; his father was business manager of a local newspaper, and a city councillor. “My family were people who liked other people, and who got along with other people,” McDonald says. “And I’ve generally found that life works better if you’re able to get along,” a view that would inform his leadership style at SNO.
McDonald met his wife at a high school dance. “We both have the same name. I was a MacDonald before I met Art,” says Janet. Art objects, “Not the same name!” “Okay,” Janet teases. “It’s M-A-C, like Sir John A. No relation.” They have four adult children and eight grandkids; in 2016, they’ll celebrate their 50th wedding anniversary. McDonald took his undergraduate and master’s degrees at Dalhousie University, while Janet went to nearby Mount Allison to study music. Janet’s father had died when she was just 10, leaving her mother widowed. “She thought a woman should have a job, in case something happened to your husband,” Janet says. Janet became a piano teacher.
It was at Dalhousie that an enthusiastic physics professor drew McDonald into the subject. “I loved how it could be used to explain how the world works,” he says. He then went to the California Institute of Technology, in Pasadena. At Caltech, McDonald rubbed shoulders with two famous scientists, Raymond Davis and John Bahcall. Although he didn’t know it then, their work on neutrinos would pave the way for SNO.
Davis and Bahcall were trying to catch neutrinos from the sun. (Neutrinos are also produced by the Earth, by dying stars, by nuclear reactors, even by bananas, which contain radioactive potassium.) In the 1960s, Davis installed a big tank of dry-cleaning fluid in the Homestake Mine in South Dakota, 1.4 kilometres underground, and watched for reactions. (Neutrinos bumping into a chlorine atom produce argon.) Based on Bahcall’s theoretical models, Davis expected to see a certain number of neutrinos. The experiment worked fantastically, except for one problem: They kept finding only a fraction of the neutrinos predicted. Where were the rest? This became known as the solar neutrino problem. “It plagued scientists for decades,” says Ray Jayawardhana, dean of science at York University, and author of Neutrino Hunters. “It was an embarrassment for physics. We didn’t understand how the sun shines.”
Back then, McDonald’s main interest was nuclear physics. After a stint at the Chalk River nuclear facility, near Ottawa, he joined Princeton University. Neil Turok, now director of the Perimeter Institute for Theoretical Physics in Waterloo, Ont., came to Princeton shortly after McDonald left, in 1989. “Art was a legendary figure among the nuclear physics group there, even then,” Turok says. The project that brought McDonald back to Canada would define his career.
Some 1.8 billion years ago, a comet slammed into the Earth, leaving a rich vein of mineral ore in what’s now the Sudbury Basin. It was here that, in 1983, a small group of scientists came to inquire about building an underground lab. George Ewan, a professor of physics at Queen’s, was one of them. “We looked at mines, and [developed] a good relationship with the people at Inco,” who owned and operated Creighton Mine, he says. (Inco is now owned by Brazil-based Vale.) Herb Chen of the University of California at Irvine had the idea of making a neutrino detector using heavy water, which is regular water with the hydrogen atoms replaced with deuterium. The problem was cost: Heavy water is expensive. Chen, who knew that heavy water is used in Canadian CANDU nuclear reactors, called up some contacts to see if it might be possible to borrow some. “To our surprise,” Ewan says, “they agreed.” In the first big victory for SNO, they managed to secure 1,000 tonnes of heavy water—worth $300 million—for free. At the first SNO collaboration meeting, in 1984, Ewan and Chen were named the Canadian and U.S. leads.
Another lucky stroke came that year with the opening of Science North, Canada’s second-largest science centre, in Sudbury. Because members of the public generally can’t visit SNO’s lab, Science North would become a conduit of information about their work and, in the early days, a way to quell local fears. “There was concern among people in Sudbury that this experiment might generate radioactivity,” says David Pearson, Science North’s founding director. In 1986, to lay fears to rest, Queen’s physicist Bill McLatchie gave a talk to Sudbury city council, and passed around a bottle of heavy water (which isn’t radioactive). At the end of his talk, he splashed it into some Teacher’s Highland Cream Scotch whisky, he says, and raised it to their good health in a “traditional Scottish toast.”
Another challenge was the size of the cavity to hold the detector. The plan was to excavate a cavern in the Creighton mine, far from mining operations, which continue today. “The SNO cavern was the biggest anyone had contemplated at that depth,” says David Sinclair of Carleton University and SNO’s deputy director. In 1985, the group submitted a grant request to do exploratory work on where the cavern might go—and were denied. They held an emergency meeting, aware the project might die. Inco agreed to do the work at cost, and Queen’s, UC Irvine, Guelph and the National Research Council of Canada scrounged up about $350,000 to pay the miners. As for what sort of vessel would hold the heavy water, Chen had another idea. On a visit to Sea World in San Diego with his daughter, he was inspired by the aquarium windows. He proposed hiring the same company to build an acrylic tank.
In 1987, Chen died after a year-long battle with cancer. It was a huge loss for the SNO team, and McDonald, then at Princeton, stepped in to fill his role. McDonald was a brilliant physicist, well-connected to the Canadian and U.S. communities, and well-liked. In 1989, with Ewan set to retire, he accepted a professorship at Queen’s. “We had to vote for a director [of SNO], and the vote was unanimous,” Ewan says. “Art was always the right man.” For McDonald, leaving Princeton was a leap of faith.
“There’s much less of a developed scientific infrastructure [here],” Turok says. “When Art said, ‘I’m going to make the world’s leading lab for neutrino physics in Canada’—well, that would have surprised a lot of people.”
On Jan. 4, 1990, the SNO project was announced in Ottawa. Scientists, engineers and contractors descended in droves upon Sudbury. “I was born and raised in this city,” said Ed Gorc, who owns Eddie’s Restaurant, a favourite of the SNO team. “Before, everything was mining. All of a sudden, you get guys coming in, renowned around the world.”
The first big challenge they faced was building the plastic acrylic tank, 12 m in diameter. “It had never been done before at that size,” Sinclair says—and built two kilometres underground, to boot. Each piece had to be lowered down, then seamlessly bonded. Sometimes the bonds would form bubbles; workers had to sand them down and start over. “That’s where I made my money,” Gorc laughs. “They couldn’t sit and watch glue dry, so they’d come up and have a few beers.”
Another problem cropped up when the detector’s 9,600 light sensors, which pick up flashes of light that indicate a neutrino has winked by, started breaking down. Nobody knew why. “It was a very acrimonious time,” says Sinclair, and could have derailed the project. McDonald pulled Sinclair off his main task, stewarding heavy water into the detector, and asked him to focus on this. He fixed it. “The fact the collaboration stayed together is a testament to Art,” he says.
Every day, on average, there were about 70 people underground working on construction, according to McDonald. They didn’t always see eye-to-eye. “The scientists are saying, ‘I want more time to make it perfect.’ The engineers are saying, ‘Make up your mind or we won’t build anything.’ If you can create a dialogue between the two,” McDonald says, “you can make something special.” McDonald got certified as a professional engineer. At meetings of the SNO collaboration, whenever possible, he sought consensus. “And if we have a 50-50 split,” he says, “we’d better talk about this longer.”
Some team members brought their families to Sudbury and settled there. Others, including McDonald, commuted. Every week, from about 1994 until the SNO experiment ended, in 2006, he’d fly to Sudbury on Monday and come back to Kingston at the end of the week, where Janet and the kids stayed. “I’m sure it was difficult. I know he was tired,” says his daughter Heather Geiger, who lives in Deep River, Ont. “My dad had to ask others to make similar sacrifices,” she continues. “I think it made him authentic, in what he was asking of his team.” Transiting through Toronto, McDonald ate so many meals at the Manchu Wok at the Pearson airport that a woman once asked him if he worked there.
Scientists in Sudbury formed a tight-knit community. Gorc says they used to scribble down equations on his bar napkins, and joked about wiring the bar TV to the detector, so they could watch neutrino reactions while having a beer. McDonald and a number of others played on a Sudbury softball team. “They were called the Neutrinos,” Janet says, “because they never hit anything.”
Stephen Hawking attended SNO’s official opening, in 1998. His speech referred to the cosmic microwave background, McDonald says, which is about three degrees above absolute zero, “and he said it’s probably almost as cold as Sudbury in the wintertime.” Hawking returned in 2012, and went underground with McDonald. A special rail car was built to transport him. “I was in the car with him and a couple of nurses. We went down halfway, at half-speed,” McDonald recalls. “And the fellow on the radio said, ‘Are you okay?’ ” Hawking indicated he was fine. “Do you want to continue?” Again, yes. “ ‘Half speed or full speed?’ ‘Full speed!’ ” McDonald laughs. “He is a very spirited individual.”
In 1999, SNO began collecting data. In 2002, the team announced their results: Neutrinos from the sun weren’t disappearing. Instead, they were oscillating, switching “flavours,” on their journey—which is why Davis didn’t catch the anticipated number. “We were able to show that we understand very accurately how the sun burns,” McDonald says. Their findings dovetailed with those of another neutrino detector in Japan. Scientists from the Super-Kamiokande (Super-K) collaboration had shown that neutrinos produced in the atmosphere were switching identities before reaching their detector. For the discovery, Kajita received the Nobel in physics alongside McDonald.
This work resolves the “solar neutrino problem” that aggravated physicists for so long. But it’s more important than that. Physics has long been governed by the Standard Model, which describes the building blocks of our universe. The Standard Model has been amazingly durable, but it said neutrinos would be massless. In fact, SNO and Super-K showed they do have mass—which is the first real indication our Standard Model isn’t complete. It offers a path toward a new model, and a new way to understand the universe.
“I can tell you,” McDonald says, remembering the day they knew what they’d found, “the party at Eddie’s was pretty big.”
The same year that SNO published its results, Raymond Davis won the Nobel Prize in Physics, alongside Masatoshi Koshiba of Japan, for the “detection of cosmic neutrinos.” SNO’s findings were cited in the Nobel announcement that year; many felt it was only a matter of time before McDonald got a Nobel of his own. “There had been rumours, but then it didn’t happen,” says Sinclair. “We all assumed the time had come and gone.” McDonald tried to put it out of his mind. “If you start counting your chickens before they hatch, you’ll go crazy,” he says. “All of us got on with doing science.”
On Oct. 6, the McDonalds’ home phone rang at 5:15 a.m. “You immediately think, ‘Who’s died?’ ” Janet says. “Then you think,” she growls, “ ‘Do you know what time it is?’ ” Art noticed the speaker on the line had a Swedish accent. The rest of the day was a blur of phone calls, interviews and heartfelt congratulations—capped off with an impromptu party at Stirling Hall, the low-slung, circular building on the Queen’s campus where the physics department is based.
In this era of big science experiments, which take teams of hundreds of people—if not thousands—there’s a feeling that a Nobel prize recognizing just three at maximum is anachronistic. “There’s a sense the Nobel is getting a little out of date,” Sinclair acknowledges. “It doesn’t cater to the realities of today.” (The Breakthrough Prize, McDonald notes, named all of the team members.) When asked the same question, Ewan, who is now a professor emeritus, becomes thoughtful. “It’s a difficult one,” he acknowledges. “I was a founder of the project, but I face facts. If we hadn’t had someone of Art’s calibre, it would never have gotten as far as it did.”
In recent years, under the directorship of Sinclair, SNO has expanded to become SNOLAB, which houses a range of experiments, further investigating neutrinos, probing supernovae, and looking for dark matter, a mysterious substance that makes up more than one-quarter of the known universe, although we have no clue what it is. The work being done at SNOLAB is just as significant, just as meticulous, as in SNO’s heyday. And it isn’t far-fetched to think this same underground lab could produce work that will, one day, win another Nobel.
SNO and SNOLAB have had a ripple effect. They continue to draw world-class scientists here, such as Caden, the particle physicist, who plans to settle in Sudbury with her husband and baby daughter. (Tellingly, all four of McDonald’s kids chose to study in Canada, three of them at Queen’s.) SNO paved the way for other big projects, Turok says, including the Perimeter Institute. “We’re trying to follow his example.” It’s a Canadian success story—one that would never have happened without an unlikely coalescence of several improbable factors, such as a deep underground mine, a fortune’s worth of heavy water provided for free, a northern Ontario town that was willing to play host, and a team of hundreds, led by one affable Nova Scotia physicist. “Everyone on the team is so happy [about the Nobel],” McDonald says. “There’s a real ‘we did it’ type of feeling. It’s exhilarating.”
But what he really wants to talk about, sitting in the SNOLAB cafeteria that day, isn’t the Nobel prize—it’s dark matter. McDonald is heavily involved in the DEAP experiment at SNOLAB, which aims to find the mysterious dark-matter particle, once and for all. Despite the endless demands on his time, he’s somehow managed to sit in on a series of meetings about it over the past two days. “It’s an exciting time for the DEAP experiment,” McDonald says eagerly. “We’re about to turn on the detector, and get going.”