Nuclear security specialist Sébastien Philippe, an assistant professor at the University of Wisconsin–Madison, has been awarded a 2025 MacArthur Fellowship.
Often referred to as “genius grants,” the fellowships are presented by the John D. and Catherine T. MacArthur Foundation to individuals based on their exceptional creativity, dedication to their pursuits and the potential for their work to benefit society — especially with additional support. Fellows receive $800,000 granted with no conditions.
Philippe became an assistant professor in the Department of Nuclear Engineering and Engineering Physics in fall 2025 after time as a research scholar at Princeton University and as a nuclear security expert with the French Ministry of Defense. Working at the intersection of science, engineering and public policy, his aim is to reduce the risk associated with nuclear weapons.
The MacArthur Foundation noted the multidisciplinary nature of Philippe’s studies of the environmental impact of nuclear weapons tests by France and the United States. The investigations combined declassified documents, historical weather reports and atmospheric modeling to show far more people in French Polynesia and New Mexico and Nevada were exposed to radiation than acknowledged in official records. The results have changed policy and the way people affected are compensated.
Today, he says, his research is more forward-looking, as the number of nuclear weapons in the world is starting to increase again. In August, Philippe was appointed to a United Nations panel charged with producing a report on the consequences of nuclear war at local, regional and global scales. It will be the first such UN report in 40 years.
“I’ve started applying my modeling tools and bringing together collaborators to better understand the consequences of nuclear weapon use and of nuclear war today,” Philippe says. “We want to see how those findings could influence domestic policy on nuclear weapons, strategies, deployments and modernization, and also inform international diplomacy on those issues.”
Philippe says he’s excited about how the high-profile MacArthur award can advance his work — and the work of others.
“I see this as an investment in the future and support for freedom of inquiry and creativity and collaboration on some sensitive issues,” says Philippe. “It gives you freedom to explore avenues that would not otherwise be easy to pursue.”
Ángel F. Adames Corraliza, associate professor in the UW-Madison Department of Atmospheric and Oceanic Sciences and Ned P. Smith Distinguished Chair of Climatology, was also awarded a 2025 MacArthur Fellowship.
“I’m thrilled for both Ángel and Sébastien, both of whom are doing such ambitious work on truly important issues: in one case, understanding the atmospheric conditions in the tropics, and in the other, understanding how we can reduce the risk of nuclear war and nuclear weapons,” says UW–Madison Chancellor Jennifer L. Mnookin. “They are both powerful examples of the kind of creative thinkers that make UW–Madison such a rich and creative research environment, and wonderful additions to our university’s proud tradition of winners of this prestigious fellowship.”
A version of this story was originally published by the UW-Madison Office of Strategic Communication.