The Royal Swedish Academy of Sciences awarded Francis Halzen the 2026 Nobel Prize in Physics on 6 October 2026. Neutrinos are elusive subatomic particles that rarely interact with matter. Because they pass through the human body unnoticed, scientists call them ghost particles. Halzen used Antarctic ice to help detect them.
Their ghost-like behaviour makes them exceptionally difficult to detect.
Neutrinos are among the most elusive particles known to science. They have no electric charge, an extremely small mass and interact so rarely with ordinary matter that trillions of them can pass through the human body every second without being noticed.
According to the Institute of Physics, their almost invisible nature has earned them the nickname "ghost particles", a description used widely by scientists, including Francis Halzen, the physicist whose pioneering work on neutrinos has now been recognised with the 2026 Nobel Prize in Physics.
The Royal Swedish Academy of Sciences awarded Halzen the prize on 6 October 2026 for his decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin. IceCube is a huge detector built into the clear ice beneath the South Pole.
What exactly are neutrinos?
Neutrinos are elementary subatomic particles. They belong to the same broad family of particles as electrons, but unlike electrons, neutrinos carry no electric charge and have an extremely small mass.
Scientists know of three types, or flavours, of neutrinos: electron, muon and tau neutrinos. Remarkably, a neutrino can change from one flavour into another as it travels. This phenomenon is known as neutrino oscillation.
The discovery of neutrino oscillations also showed that neutrinos have mass. Takaaki Kajita and Arthur B. McDonald received the 2015 Nobel Prize in Physics for the discovery of this phenomenon.
Why are they called 'ghost particles'?
Neutrinos are extremely difficult to detect because they interact with matter only very weakly. Unlike charged particles, they are not deflected by magnetic fields and can travel enormous distances without being absorbed.
According to CERN, a neutrino can travel through around a light-year of lead before interacting with matter. The Sun alone sends about 100 trillion neutrinos through our bodies every second.
That ability to pass through matter almost unnoticed explains the ghost-like description. Scientists cannot simply observe a neutrino travelling through space. Instead, they wait for the rare occasions when one interacts with another particle.
How does IceCube find them?
Halzen's key idea was to use the vast volume of transparent Antarctic ice as a neutrino detector.
IceCube has thousands of light sensors embedded deep beneath the South Pole. When a neutrino happens to interact with matter in the ice, it can produce charged particles which create a tiny flash of light. The sensors record that light and allow scientists to estimate the neutrino's direction and energy.
The observatory occupies roughly a cubic kilometre of Antarctic ice. Its observations have allowed researchers to identify high-energy neutrinos arriving from beyond our Solar System and investigate their possible cosmic sources.
Why are neutrinos important?
Neutrinos can provide information that ordinary telescopes cannot. Because they rarely interact with matter and are not electrically charged, neutrinos can escape from violent cosmic environments and travel vast distances in relatively undisturbed form. Scientists therefore use them as a new way of studying some of the most energetic events in the universe.
IceCube's discovery of high-energy astrophysical neutrinos in 2013 helped establish neutrino astronomy as a new field. Later research has produced evidence linking neutrino emission to galaxies including TXS 0506+056 and NGC 1068, also known as Messier 77.
For Halzen, the significance goes beyond finding a difficult-to-detect particle. His work has helped open what scientists describe as a new window on the universe. The basic paradox of neutrinos remains what makes them so valuable: they are almost impossible to see, yet they can carry information from some of the most distant and violent places in the cosmos.
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