A US physicist has recently shed new light on the mysterious particles behind the 2026 Nobel Prize in Physics, and explained that they could help solve some of the universe’s greatest secrets.
George Fuller, a distinguished professor at the University of California San Diego (UC San Diego), worked with Francis Halzen, PhD, on an early study involving the IceCube Neutrino Observatory. The Belgian-American physicist earned this year’s physics Nobel for his work on the project.
Now Fuller revealed how they travel across the universe and what makes them so difficult to detect. Approximately 100 billion neutrinos pass through each square centimeter of our bodies every second. Most of them leave no trace.
Fuller emphasized the importance of understanding neutrinos. “Halzen’s work, and the work of those he inspired with his vision, was foundational in giving humanity a new window on the universe and on the mysterious and notoriously slippery neutrino,” he added.
Detecting ghost particles
The IceCube is the world’s largest neutrino detector. Positioned in Antarctica, near the US Amundsen-Scott South Pole Station, it relies on thousands of light sensors buried in holes drilled through about 0.24 cubic miles (one cubic kilometer) of ice to detect neutrinos.
The observatory was developed following Halzen’s vision in the 1990s of building a detector deep beneath Antarctica’s surface. At that depth, fewer air bubbles and impurities would interfere with measurements.
But spotting these elusive particles requires extraordinary equipment since they interact so weakly with matter. As a result, the site uses a massive volume of the ice to capture signs of them.
Credit: Sven Lidstrom, IceCube / NSF
When a high-energy neutrino hits the ice, it can release charged particles, which generate faint flashes of blue light known as Cherenkov radiation. These flashes can determine the neutrino’s energy and the direction it traveled from.
Still, high-energy cosmic neutrinos are extremely rare. IceCube detects only a few dozen each year. Some have 10 billion times more energy than typical neutrinos produced by the Sun. “One detected by a similar experiment has an energy 200 times higher than that,” Fuller said.
Even so, their origins remain unknown. “We don’t really know where that neutrino came from,” Fuller said. “The fact that it got here at all may be saying something profound about the universe.”
Secrets of the universe
As elementary particles, neutrinos can’t be broken down into smaller parts. There are three types of neutrons: electron, muon, and tau. As they rarely interact with matter, they can travel enormous distances through space at nearly the speed of light.
“Neutrinos are truly ghost-like particles,” Fuller noted. “It’s hard to stop them. It’s hard to catch them. How do we even know they exist or where they are?” At the same time, their unique properties allow them to escape extreme conditions near collapsing stars and black holes.
According to Fuller, neutrinos can even travel through light-years of lead without stopping, depending on their energy. Despite being so difficult to detect, these particles are incredibly abundant. Estimates suggest there are around one billion neutrinos for every atom in the cosmos.
“In that sense, Halzen really is at the frontier of experimental fundamental particle physics,” the physicist concluded in a press release. New discoveries could reveal more about the Big Bang and the early universe.
UC San Diego is also part of the Simons Observatory in Chile’s Atacama Desert, which studies the cosmic microwave background, the oldest light in the universe, and could also provide clues about ancient neutrinos.