IceCube, high-energy neutrinos, and Francis Halzen win 2026’s Physics Nobel

There’s a whole entire Universe out there, and the more we learn about it as it actually is, the greater our potential becomes to achieve great things as a civilization, even if the path from knowledge to improving humanity is far from clear. The Nobel Prize was set up more than 100 years ago with the express purpose of rewarding those whose work provides the “greatest benefit to humankind” in a number of disciplines, including physics. We couldn’t foresee that: Similarly, we cannot know what advances will arise in the future from advances made today in fields like elementary particle physics, gravitational waves, or neutrino astronomy, but possibilities range from computational advances to superior timekeeping technologies to extraterrestrial communication.

One thing is certain, however: we have to make the fundamental advance, first, if we ever hope to find out. In many ways, that’s what the science of physics is all about. It’s for that reason that the world ought to be incredibly excited that the 2026 Nobel Prize in physics has gone to Francis Halzen, for “decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin,” which is a remarkable testament to what a single individual can accomplish with a creative idea, a lot of hard work and organization, persistence, a strong national investment in science, and quite a bit of good luck.

Here’s the story of this remarkable advance in neutrino physics and astrophysics. The remnant of SN 1987A, located in the Large Magellanic Cloud some 165,000 light years away. It was the closest observed supernova to Earth in more than three centuries, and reached a maximum magnitude of +2.8, clearly visible to the naked eye and significantly brighter than the host galaxy containing it.

Four hours prior to the light arriving, a burst of about two dozen neutrinos were seen in three detectors on Earth, with Kamiokande detecting the greatest number of neutrinos, 12, across a span of about 13 seconds. The idea of IceCube was born 39 years ago, back before “neutrino astrophysics” was a field that went beyond our Solar System. Prior to 1987, neutrino astrophysics was restricted solely to measuring the neutrinos coming from within the Solar System: by building a large tank of fluid deep underground.

Starting in 1968, the idea was that neutrinos from the Sun, occasionally, would interact with an atomic nucleus, transmuting a neutron into a proton, and converting the neutrino into an electron in the process. By looking for the newly transmuted nuclei, solar neutrinos could then be detected. In principle, nuclear reactions would occur all across the Universe, releasing neutrinos when they did, but the flux would be far too low to detect them.

However, due to contemporaneous interest in grand unified theories, particle physicists had begun building much larger tanks of fluid surrounded by photomultiplier tubes, with the idea being to detect any spontaneously decaying protons by measuring their faster-than-light in the liquid medium radiation: Cherenkov radiation. The major experiment of the 1980s, Kamiokande, was originally an experiment to search for nucleon decay in Kamioka, Japan. Running for several years, it only obtained null results, until the day of February 24, 1987.