Starry nights planted seeds of wonder in world-leading physicist

“I think my passion for physics started when I was six years old,” she said in an interview at the Waterloo institute, which is celebrating its 25th anniversary this year.

Carena was the only child in a family of Italian and Spanish migrants who came to Argentina in the early 20th century.

Her father’s family migrated around 1913 and built a cattle and grain operation on the Pampas. When he wasn’t working, her father played guitar, violin and a type of accordion called a bandoneon. Then, he was off to Buenos Aires for his military service.

There, he met his wife . She was from a Spanish family that came to Argentina in 1904. So Carena’s young life was split between life on the Pampas riding horses, swimming, staring at the Milky Way and nine months of school every year in Buenos Aires. During the school year, she lived with her grandmother.

“She was a beautiful role model for me. I was very attached to my grandmother and she was also a very strong lady,” said Carena. “She came from Spain when she was 14 years old, alone.”

Carena remembers excelling at ballet. She wanted to attend a special school to purse it. But Argentina was going through what was dubbed the Dirty War, with months of government-organized anti-communist suppression leading to a military coup in March 1976. The junta killed thousands of trade unionists, communists, independent journalists and pro-democracy politicians. There was a lot of violence.

“At 12, I had to make a decision for my mom — maybe for me, to be honest — to go to the religious school,” said Carena. “Ballet is something that inspires me a lot. If I had gone down that path, probably we would not be talking today.”

Amid that political unrest, Carena’s mother did not want her travelling across the city every day to and from ballet school.

Carena’s mother sent her to an all-girls’ Catholic high school instead. It was there a talented math teacher inspired Carena, told her to question everything and encouraged her to study math after high school. To this day, the world-renowned physicist points to that “amazing math teacher” as a critical influence in her life.

The math teacher told her about a place in the foothills of the Andes mountains called the Instituto Balseiro. Students need two years of post-secondary studies in engineering or physics before they can apply. The Instituto Balseiro produced Argentina’s top physicists.

After high school, Carena studied engineering at ITBA — the Instituto Tecnologico de Buenos Aires. That’s where she met Carlos, her future husband, and together they read books by Jorge Luis Borges, the great Argentinian writer of short stories, poetry and essays.

“The short fiction by Borges, I loved the ‘Garden of Forking Paths.’ There are many stories where science and the literature get together,” said Carena. “I love art, and I love literature and Borges somehow inspires me, especially with this book.”

She realized designing bridges was not for her, but she was reluctant to drop engineering altogether. So, in her second year, she continued at the Instituto Tecnologico but also studied philosophy at the University of Buenos Aires.

She was one of eight women in the engineering class of 160.

“So, it was a bit challenging as a young adult to manage that world,” she said of that male-dominated environment.

But she had done it before. Her father would bring her to cattle auctions on the Pampas. The other ranchers brought their sons, but Carena liked the auctions because they were so different from her other lives in the big city or even on the ranch. 

Her mixture of engineering and philosophy courses led to physics, she said. And in 1982, she was accepted at the Instituto Balseiro, where she was one of three women in a class of 33.

“Being part of the different group makes things more challenging. On the other hand, it makes you stronger,” she said of being one of the few women. “I am happy things have evolved quite a bit in the right direction.”

It was here Carena learned about quantum mechanics — a branch of physics that describes the behaviour of subatomic particles — as well as high-level math and experimental physics. What she learned at the Instituto Balseiro would reverse the migration routes of her grandparents, taking her to universities in Hamburg, Munich, Switzerland, Chicago and, now, the Perimeter Institute for Theoretical Physics.

Carena and Carlos married in 1985. They had diplomas from the Instituto Balseiro, the equivalent of a master’s in North America. They left for the University of Hamburg in September 1987 to do PhDs at the largest particle accelerator in Germany — the Deutsches Elektronen-Synchrotron.

Particle accelerators are giant, high-tech tubes that send subatomic particles speeding into walls or crashing into each other. Physicists learn a lot about the particles when that happens. The scientists are dubbed “atom smashers.” Marcela was featured in a documentary with that title.

Growing up in Argentina during the Dirty War was very hard, and working in West Germany in the 1980s, when memories of the Second World War and Holocaust were much fresher, left deep impressions on Carena.

“My amazing land lady in Hamburg, who treated us so great, we talked a lot about what happened in Germany and she lived through that,” said Carena. “As a scientist especially, we should try to be very conscious that we open the door to those who may be in need.”

Before leaving West Germany for a post-doc teaching appointment at Purdue University, Carena, Carlos and some friends drove to West Berlin and crossed into Communist East Germany at Checkpoint Charlie. That was just months before the Berlin Wall came down in 1989, and the former Soviet Union started to collapse.

One of the biggest particle accelerators in the world is at CERN — the European Organization for Nuclear Research in Berne, Switzerland. And in 1993, Carena took a research fellowship there at one of the most exciting times and places in the world of theoretical physics — the search for what became known as “the God particle.”

She was pregnant with their first child, Sebastian, but did not share that with her research colleagues. There were no other pregnant women working at CERN, and she feared her commitment to the research would be questioned if she told people about her pregnancy. It was 1995.

Carena and Carlos stayed at CERN until 1998, when she was appointed as a scientist at the Fermi National Accelerator Laboratory in Batavia, Ill., near Chicago. And 10 yeas later, she was teaching at the University of Chicago as well.

Her office there overlooked Stagg Field at the University of Chicago where Enrico Fermi staged a historic experiment — he built a pile of graphite and uranium six metres high under the stands in December 1942. Fermi created the first sustained and controlled nuclear chain reaction. It was a milestone experiment in the Manhattan Project, the U.S. program to build the atomic bomb.

And 70 years later, Carena gathered her family and colleagues together in Chicago to watch a famous news conference out of CERN about the discovery of the Higgs bosun particle — one of the fundamental building blocks of the universe.

Every particle physicist knows where they were on July 4, 2012. Carena, her two sons, her husband and more than 30 colleagues gathered at her house to watch the news conference at 2 a.m. Carena watched her friend and colleague, Fabiola Gianotti, present some of the evidence for the historic discovery. Gianotti is the fist woman appointed CERN’s director general.

When they watched the announcement, Carena’s boys were youngsters. Now, like their parents, they are highly educated and pursuing careers in science.

Julian, 23, just started his PhD in neuroscience at the University of California in San Francisco. Sebastian, 29, works in cosmology and astro-particle-physics and is doing post-doc research at the Flat Iron Institute in New York.

“They are the best thing I have in life — really, they are,” said Carena. “I am so proud of them, and I have to say I am super proud of them because they are amazing scientifically and so on, but the reason I am most proud of them is they are amazing human beings. For me, one thing cannot go without the other.”

The unstructured research environment at the Perimeter Institute is quite unique, she said, and physicists are looking at fundamental questions about the universe. She was part of Perimeter’s scientific advisory panel for the past four years, so she knew it well before her appointment in November 2024.

Her research focus is dark matter.

“We know dark matter is 85 per cent of the matter in the universe and we don’t have a clue what it is made of,” said Carena.

Answers may be found 1,000 metres underground in an old mine in Sudbury, where the Sudbury Neutrino Observatory (SNO) was built in the 1990s. The scientists behind the observatory won a Nobel Prize in Physics.

Neutrinos are subatomic particles made inside stars, and the universe is full of them. The SNO project discovered three different types of neutrinos, each with a different mass. In the time it takes to read this sentence, several have passed through your body. But the scientists at SNO ruled out neutrinos as the mysterious dark matter.

So, the search continues, and Carena is already thinking about experiments that will have Perimeter and SNO collaborating.

“I am excited to be here,” she said.