Four facilities now emulate 1-square-kilometer Antarctic array

The 2026 Nobel Prize in physics traces a 96-year arc of particle physics research, from Wolfgang Pauli’s 1930 prediction of an undetectable particle to the IceCube Neutrino Observatory’s capture of high-energy cosmic neutrinos in the Antarctic ice. The Royal Swedish Academy of Sciences on Tuesday awarded the prize to Francis Halzen, the University of Wisconsin physicist who has led the IceCube collaboration for decades.

Pauli first introduced the idea of neutrinos in 1930, according to Dr. Mark Pearce of Particle Physics, Astrophysics & Medical Imaging in Stockholm. “I have done a terrible thing. I have postulated a particle which cannot be detected,” Pauli said of his prediction. Pearce described neutrinos as “ghost-like messengers from the cosmos.” In 1956, scientists Clyce Cowan and Frederick Rhinds confirmed the neutrino’s existence by using a nuclear reactor to emit the tiny particles, Pearce said.

IceCube equips 1 square kilometer of Antarctic ice with sensors that detect the flashes of light made when a neutrino collides with other atomic particles. Neutrinos are tiny, neutral particles emitted from the sun that flow through all matter without being stopped; millions pass through the human body — without changing or losing energy — at all times without being felt. The detector was completed in 2011, and scientists saw the first evidence of high-energy neutrinos two years later, Pearce said.

Halzen was traveling through Italy for a committee meeting when the call from Sweden reached him. “It was a great surprise, and I obviously didn’t expect it,” he said on the phone with Dr. Ellen Moons, science professor and secretary general of the Royal Swedish Academy of Sciences. “I’m traveling through Italy for a committee meeting. But it’s a great pleasure to hear about this prize.”

He credited the broader collaboration that built IceCube. “I hope this prize will reflect on the credit that this large collaboration, and especially some very critical people who made critical, decisive contributions to this project over time,” Halzen said. “And I would like to point out that this project started as a collaboration of UW-Madison and Berkeley, but the first people who joined this project at a very early stage were the universities of Uppsala and Stockholm [in Sweden].”

Halzen was joined by more than 450 scientists in what he called an adventure where success was not guaranteed. “When I reflect on this at this moment, I have to emphasize how lucky I was, because when we started this project, you know, everybody realized this was maybe a good idea, but very few thought it would work, including myself,” he said. “So, this was kind of an adventure where success was not guaranteed, and we were lucky to overcome the various challenges, partly because of the talent of collaborators, and partially because of luck.”

Halzen learned of the prize days after a science festival in Bergamo, Italy, had already announced that he would win. “Well, it feels strange. I was last weekend at a science festival in Bergamo [Italy], where they essentially announced that I would win the Nobel Prize, and it always made me feel very strange,” he said. “And it makes me [feel] even more strange when it becomes true. But I think for me, the main pleasure of it, besides winning the Nobel Prize, is that I hope this reflects on the really courageous people who joined me in the beginning of this project. When you know, I cannot say this now, but no really respectable conservative physicist would have joined me, but many talented people did, and that’s why I’m here.”

Halzen is from Tienen, Belgium, and received his master’s and doctorate degrees from the Catholic University of Leuven. He worked at CERN in Switzerland from 1969 to 1971, then visited the University of Wisconsin for six months in 1971. “And I’ve been there ever since,” he said.

“Wisconsin is a unique place in the sense that the university maintains the type of facilities where you can do experiments like IceCube, and so I was lucky also to be in the right place when this idea came along,” he said.

A reporter asked whether neutrinos could be used to receive messages from other civilizations in outer space; Halzen said friends had already proposed the possibility. “But I don’t think I will go there,” he said. “I think we have enough realistic problems to deal with right now, and you know, make neutrino astronomy a reality rather than worry about this.”

Four other facilities around the world are now emulating IceCube to continue research on neutrinos.