Francis Halzen, a physicist at the University of Wisconsin, Madison, has won the 2026 Nobel Prize in Physics “for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.” Halzen spearheaded the development and construction of the IceCube Neutrino Observatory in Antarctica, enabling physicists to capture high-energy neutrinos created in the distant universe. And while the Nobel was awarded to Halzen alone, he emphasized that his work was the result of a “large collaboration” with other researchers. But many talented people did, and that’s why I’m here,” he said.
It has transformed our understanding of the universe by detecting the first high-energy neutrinos from beyond our galaxy, opening an entirely new field of neutrino astronomy. The experiment is the extraordinary achievement of hundreds of scientists, engineers, and collaborators, but Francis was the person who dreamed big enough to imagine an experiment of this scale and then relentlessly pushed to make it a reality.” As previously reported, neutrinos travel near the speed of light. John Updike’s 1959 poem, “Cosmic Gall,” pays tribute to the two most defining features of neutrinos: They have no charge, and for decades, physicists believed they had no mass (they actually have a teeny bit of mass).
Neutrinos are the most abundant subatomic particle in the universe, but they very rarely interact with any type of matter. We are constantly being bombarded every second by millions of these tiny particles, yet they pass right through us without our even noticing. That’s why Isaac Asimov dubbed them “ghost particles.” That low rate of interaction makes neutrinos extremely difficult to detect, but because they are so light, they can escape unimpeded (and thus largely unchanged) by collisions with other particles of matter.
This means they can provide valuable clues to astronomers about distant systems, further augmented by what can be learned with telescopes across the electromagnetic spectrum, as well as gravitational waves. Together, these different sources of information have been dubbed “multimessenger” astronomy. Neutrinos were first proposed by Wolfgang Pauli in a 1930 letter to colleagues.
He was trying to explain some baffling experimental results on radioactive beta decay in atomic nuclei, where energy appeared to be missing—something he deemed (correctly) to be impossible. He thought a new kind of subatomic particle with no charge and no mass may have carried away the missing energy; it was Enrico Fermi who later dubbed it a neutrino.
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