Francis Halzen, a Belgian particle physicist at the University of Wisconsin–Madison, has been awarded the 2026 Nobel Prize in Physics for the IceCube Observatory and its discovery of high-energy astrophysical neutrinos. The Nobel committee announced the prize on October 6. It carries 12 million Swedish kronor and is the first Nobel in physics awarded to a single person in 34 years.
Neutrinos are among the most elusive particles known. They carry no electric charge, have almost no mass and interact with ordinary matter only through the weak force, which means trillions pass through the human body every second without leaving a trace. Physicists come in three types, or flavours, of neutrino, electron, muon and tau, and they can switch between these flavours as they travel. The particle was first proposed by Wolfgang Pauli in 1930 as a way to preserve the principle of energy conservation in certain radioactive decays, and it was not directly detected until 1956, when Frederick Reines and Clyde Cowan picked up neutrinos streaming from a nuclear reactor.
Earlier Nobel prizes had already recognised neutrino work. Raymond Davis and Masatoshi Koshiba were honoured for detecting neutrinos from the Sun and from a supernova, and Takaaki Kajita and Arthur McDonald for showing that neutrinos change flavour. Halzen's award differs in focus. It recognises the detection of neutrinos from sources far beyond our own galaxy, opening a new window on the distant universe.
Those cosmic neutrinos are produced when high-energy protons from space collide with other particles, creating pions that decay into a chain of lighter particles, including neutrinos. Because the observatory cannot see these particles directly, IceCube uses a large array of optical sensors buried in the Antarctic ice. When a neutrino interacts with the ice, it produces charged particles that emit faint flashes of Cherenkov light, and the sensors record those flashes to reconstruct where the neutrino came from.
Credit. Based on reporting by Samreet Dhillon for bohring.substack.com. Is this your work? Write to us.
25
