I run a physics lab – and thousands of kilometers a year

I run a physics lab – and thousands of kilometers a year

Rear view of Jenny running down a long straight road in Utah on a sunny day

Physicist Jenny Hoffman ran the long way through Utah on day 11 of her record-breaking journey across the United States.Credit: Jill Yeomans

Profiles of working scientists

This article is part of a case Nature series in which we profile scientists with unusual career histories or outside interests.

Jenny Hoffman made a last minute decision to embark on a new attempt to run across the United States, coast to coast, in pursuit of a world record. A physicist at Harvard University who studies the properties of insulators and conducting materials, she turned to the time-honored method of recruiting students willing to help. In just two weeks, she gathered an enthusiastic team to accompany him along the way, supplying him with food, water and emotional support.

Hoffman took a break, left her lab under the care of a senior research scientist, and set off from San Francisco on September 16, 2023. Her 3,000-mile (4,888 km) route took her through California, Nevada, Utah, Colorado, Nebraska, Iowa, Illinois, Indiana, Ohio, Pennsylvania, New Jersey and New York. Sleeping in a camper van that followed her along the way, she averaged more than 100 kilometers a day as she navigated highways with narrow shoulders, storms, dogs and even large pieces of farm equipment that nearly drove her off the road. .

Just 47 days, 12 hours and 35 minutes later, Hoffman arrived at New York City Hall. In the last kilometers, she was accompanied by dozens of friends, family and fans. Her time broke the previous women’s record by more than a week. She returned victorious to Harvard’s physics department in Cambridge, Massachusetts. Less than a month later, she flew to Taiwan to compete in the 24H World Championships, an international 24-hour race in which she placed 23rd in the world.

Now, Hoffman is back in the lab, writing grant proposals in an office her colleagues have decorated with balloons and trying to regulate her metabolism after consuming 8,000 calories a day during competitions. She’s also trying to decide on her next big goal, which may not be an athletic one. “You can have a scientific impact, but you can also have an impact by being a good mentor or giving someone the confidence they need to do a hard thing,” she says. “People’s influences are probably more accessible to me now.”

Double duty

Many scientists would worry that the intense training required to achieve an extreme athletic goal would affect their research results. But Hoffman is no slouch. Her laboratory has published dozens of papers, including one in science last March about quantum oscillations in a type of insulating material1. She mentors students in her lab and others, and attends numerous conferences. “I don’t think there’s any compromise in any dimension of her life,” says Daniel Lieberman, an anthropologist at Harvard who studies the evolution of human athleticism and runs with Hoffman every Tuesday morning. “I don’t think she sleeps.”

Hoffman insists she sleeps — about seven hours a night — but says running is a necessary function of life. “It’s just part of the self-care I do every day,” she says. “Even if you have a grant due tomorrow, you’re going to brush your teeth, right?” Tracking her time and looking for ways to make things more efficient helps, although she admits she doesn’t have time for a social life beyond her husband and three children.

Jenny, wearing a red 'USA' T-shirt, runs during the Taipei 24 Hour World Championships

A few weeks after completing her cross-country run, Jenny Hoffman competed for Team USA in the 24-hour World Championship 24H event in Taiwan.Credit: Howie Stern

She often worries that she is neglecting either her career or her sports activities. “There’s this myth of having it all or doing it all and you can’t,” she says. “I’m definitely not as good a physicist as I would be if I didn’t run, and I’m not as good a runner as I would be full-time. But you only get one life, and I don’t want to throw any of these activities away.”

Running has been a part of Hoffman’s life for more than 30 years, although she only began to pursue it seriously in 2014, after the birth of her third child. She never expected to be successful. But she soon found herself winning ultramarathons — races that are 50km, 100km and longer — and her goals became increasingly difficult. Her 2023 run across the United States was her third attempt, following a particularly heartbreaking attempt in 2019 when she injured her knee with just 800 kilometers to go.

Teamwork makes the dream work

The latest run couldn’t have happened without a lot of teamwork, Hoffman says. During the most intensive two weeks of training, the amount of time she spent in the lab was cut in half, but she trusted her group of about 30 people to continue the science. “I’m really lucky to have a great group of students who work together as a team really well and they’re able to turn to each other for questions and advice,” she says. The team, she says, was used to working without her being physically present as a result of the COVID-19 pandemic, and her senior scientist was able to fill in for her, handling the issues.

The training and running itself also required a team, which included Hoffman’s husband as well as massage therapists and a professional logistics coordinator, along with a support team drawn from students and old friends. Among them was Yanting Teng, a Harvard physics student who signed up to drive Hoffman’s support van in Iowa and Illinois. Teng was particularly impressed with Hoffman’s drive to reach her next stopping point each day and her willingness to push further if she wasn’t satisfied with her progress that day. “If she wants to do something and feels good about it, she’ll go for it,” Teng says. “I’ve never seen anyone so determined.”

Jenny, wearing a hi-vis top and a head torch, poses with Yanting Teng, a graduate student in physics at Harvard

Graduate student Yanting Teng (right) helped support Jenny Hoffman’s team for part of the trip.Credit: Jill Yeomans

Determination can be the key to being a good ultrarunner—and a good scientist, Hoffman says. “You have to be okay with repetition to be successful in the lab, and sometimes you have to repeat a task many times to get it right,” she says. “I think the same kind of mentality applies to long-distance running.”

Science itself supports this assessment. Although little research has been done on ultrarunners, Lieberman says mental toughness and pain tolerance are the most necessary traits, in addition to good form and endurance. The human body evolved to run long distances instead of short sprints, he says, but land mammals did not evolve to run Hoffman’s average of 101 kilometers per day. “No horse can do what Jenny did,” he says. “You would kill the horse.”

For Hoffman, long-distance running is not only a personal challenge, but also a necessary escape. Many people with demanding careers find that they think more clearly when they run or exercise, describing it as a chance to clear their minds and think about problems in a new way. But Hoffman says she never thinks about physics while running. Instead, she listens to audio books.

In fact, Hoffman says, the objective nature of the sport puts her day job into perspective. “Human judgment plays a big role in science and much less of a role in running, so I really appreciate being able to do something where someone else’s opinion doesn’t matter,” she says. “There are no anonymous reviewers. I just run the time I run.”

Rapid fire questions and answers

What was the best thing you saw on your run across the United States?

Eccles Canyon Pass in Utah. The sun was rising just as the full moon was setting on the other side, and the fall foliage was perfect. It was just wonderful. But there is much beauty in this country. Even the cornfields are beautiful, walking into them on a sunny day and seeing the waves of golden wheat.

What equipment did you need?

I went through 11 pairs of running shoes, changing them every 2-5 days, depending on road conditions. I also wore two watches – one on each wrist – so that I had backup data for tracking for the world record. Here’s something I’m proud of: I made it across the country with US$7 worth of socks. I bought a 16-pack of socks at Walmart and we did laundry, so it took me all over the country.

What do you listen to while running?

I usually listen to books. I love history and memories. Right now, I’m listening to the memoir of elite runner Lauren Fleshman, Good for a girl (2023), which talks about sports science for women and how most sports science is actually measured in men.

What do you like to eat while running?

I don’t have very specific meal plans; this is a weak point for me. When I was running across the country, I ate eight eggs a day and salad, but also a ton of junk food. Of the 8,000 calories I ate each day, maybe half of them were junk food.

What is your favorite food?

I don’t like to buy food in convenience stores because the quantities are very small. I love buying junk food at the grocery store where you can get a big bag of M&Ms. Chocolate is my weak point. I eat a lot of baked goods, too, all to get calories.

What’s your best mentoring hack?

I think people do their best work when they are happy and confident. I try to speak positively about the work of my team members in direct conversation with them – and I also try to speak positively about each of my students ‘behind their backs’ when talking to other students. It is very important that my students value each other so that they can work together to solve problems even when I am not immediately available. To maintain this teamwork, I take their input very seriously whenever I consider bringing a new student onto the team.

I also try to provide enough resources for students to act independently and minimize emails. This includes guidance on everything from keeping a good lab notebook to navigating international visas. And I have a ‘getting started’ guide to communication that can help alleviate frustrations. For example, I tell new students to be ‘squeaky wheels’ if it helps to efficiently answer their questions.

What is your favorite scientific discovery?

I am very proud of one Physics Review Papers cover article2 that actually showed up on my birthday in 2022 – best birthday present ever! We invented the first topological acoustic transistor, which can efficiently turn sound transmission on or off. It is part of our broader work using acoustic metamaterials to simulate quantum materials and devices. Transistors can lead to improvements in areas such as one-way sound transmission, ultrasound imaging, and echolocation.

This interview has been edited for length and clarity.

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