“I love creating explosive reactions – it's my thing”

Pierre Wets - 2024 EPFL/Julie Haffner - CC-BY-SA 4.0
Pierre Wets is part physicist, part stage director. For over 20 years, he’s been inventing, reinventing, preparing and running physics experiments for the education (and delight) of EPFL’s students.
Physics experiments are always a big hit at EPFL’s open house and Scientastic festival, among children and adults alike. Yet the oohs and aahs from the audience reflect not only the amazing science on display, but also the work done by the experts who design and put on the experiments.
Wets is one such expert. He was working as an electrical engineer when he learned about this job opportunity at EPFL – and jumped on it. “What I missed working in industry was the research and discovery involved in physics,” he says.
Wets unwittingly got his first hands-on experience with chemical reactions while he was a physics lab assistant at the University of Lausanne. “One day, my supervisor asked me to refill the containers of acid used to dissolve the copper in circuit boards,” he recalls. “But I used the wrong container and ended up pouring the acid into metal drums. The drums began to leak a few hours later and covered the floor with a toxic, staining liquid. You can probably still see the marks on the lab floor!”

Knowledge, creativity and tinkering
The physics reactions that Wets and his two colleagues – Julien Burnens and Didier Klopfenstein – put on are intended partly to wow the audience, but mostly to educate them. The three experts design experiments to illustrate scientific phenomena, pique students’ curiosity and give them the keys to better understanding the theory they’re taught in class.
EPFL has a catalogue of around 700 experiments. Wets and his colleagues update and improve dozens of them each year and add a few new ones – whether on their own initiative or at the request of an EPFL professor. “Professors come to us with an aspect of theory that they’d like to demonstrate, and we provide our pragmatic experience and intuition,” says Wets. “We put our heads together and decide on an experiment that will both illustrate the theory and give students something practical, visual and interesting.”
Does Wets find it frustrating to boil the nuances of theory down to a single experiment? On the contrary, he explains: “You can cover a lot of material in a single experiment. There are trade-offs to be made, but we always try to stay as close to the theory as possible.”
Faithfulness and accuracy are his watchwords – and he thinks it’s an advantage that he’s not a physicist by training, because it means he can take a more objective view. “Since we don’t delve into the theory, we don’t limit a phenomenon to a given formula,” says Wets. “Instead, we encourage students to observe what happens with their senses.”

Marking minds
Wets gets out of his lab several times a week to perform experiments directly in front of students. Sometimes he creates smoke, fire or even an explosion. The students’ undivided attention is always guaranteed. “My experiments focus the attention of the whole classroom. Students are really present and they watch with all their senses on alert.”
Even after two decades in this role, Wets is just as enthusiastic as ever. “I often come across intriguing new experiments, and since I’m the kind of person who always wants to know how things work, I try to get to the bottom of the phenomenon taking place,” he says. “Once I’ve understood it, I can go back and watch the experiment and appreciate its beauty.”
If he had to pick a favorite type of experiment, it would be those involving light – he spent a few years working on laser systems – and those he developed himself. And Wets admits that his “thing” is fire and explosions. “One of our experiments entails filling a balloon with hydrogen and popping it,” he says. “Once I tried to do the same thing with propane, but the result was very different. Propane gas is a hydrocarbon that’s heavier than air. It slowly caught fire and literally went down in flames, right on top of me!” Do not try this at home.
Wets has a clearly unquenchable thirst for knowledge. Take this interview, for example – when it was over, he turned the tables and questioned our cameraman on the best way to capture quality images.