Ice ice baby: finding the origin of the universe using subatomic particles and ice

This curiosity column explains the 2026 Nobel Prize in physics

By NAREN KRISHNA JEGAN — science@theaggie.org 

The 2026 Nobel Prize in physics was awarded to Dr. Francis Halzen, a theoretical and experimental physicist at the University of Wisconsin–Madison, on Oct. 6 for “decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin,” according to The Nobel Prize Organization.

Neutrinos are neutrally-charged subatomic elementary particles. Unlike commonly studied subatomic particles like neutrons, protons or electrons, which have no charge, a positive and a negative charge, respectively, neutrinos do not experience the same set of interactions that allow physicists to easily detect them.

Dr. David Saltzberg, an experimental particle physicist at UCLA, explained the forces and interactions that neutrinos experience. 

“One can think of a neutrino as an electron that has lost its charge,” Saltzberg said. “Because the usual way we detect electrons is through electric and magnetic forces, that option is unavailable for neutrinos. These forces are not something we encounter in everyday life, but they exist, and are responsible for part of the nuclear reactions in the Sun. But they are really really weak, and that is why these neutrinos can go through thousands of miles (or more) of material without being stopped or losing any energy.”

Studying neutrinos offers physicists insight into astronomy occurring in regions that are difficult to study due to existing light telescopy methods. Dr. Alexander Kusenko, a theoretical physicist at UCLA, explained why physicists are interested in neutrinos as a tool for astronomy.

“Neutrinos can come from regions opaque to light, such as the solar core, a collapsing massive star, or environments close to a supermassive black hole swallowing gas and stars,” Kusenko said. “They can bring us information about the inner workings of the most powerful sources of radiation in the universe.  While other particles, such as protons, are deflected by magnetic fields, neutrinos point straight back to their sources. All of this makes neutrino astronomy an exciting emerging field of science.”

The IceCube Neutrino Observatory is a collaboration between 450 researchers across 58 institutions in 14 countries. Led by Halzen, the observatory studied the detection of neutrinos in the South Pole. 

Saltzberg explained the reasoning behind using the South Pole as the home to the laboratory.

“Since the neutrinos are so weakly interacting, you need a big, thick detector to find even a small number of them,” Saltzberg said. “Francis Halzen and others calculated you would need a cubic kilometer or more of material. So you have to use naturally occurring material and it must be highly transparent so you can see where the neutrinos interacted. That's why South Polar ice is so wonderful. It approximates frozen, clean, distilled water.”

Halzen and his team drilled holes into Antarctic ice and attached them to strings of neutrino detectors. Kusenko explained how these detectors are able to produce meaningful signals to the IceCube physicists.

“When a neutrino interacts in ice, it produces charged particles and light, which is detected by the IceCube's electronic sensors and later analyzed by scientists,” Kusenko said. “The results tell the scientists about the energies of these neutrinos and the location of their sources.”

In recent years, the IceCube team has grown from discovering the first instance of cosmic neutrinos, discovering neutrino signals from galaxies nearly 50 million light-years from Earth and later creating a map of the Milky Way galaxy using neutrinos.

Saltzberg shared his perspective on future research possible from Halzen’s and the IceCube collaboration’s research.

“The field is still in its infancy but I am optimistic we will learn a great deal by peering into these astronomical sources with neutrinos,” Saltzburg said. “And we may get lucky and these neutrinos will tell us something about the mysterious invisible matter that makes up 90% of the matter of the universe, which we don't know nearly anything about.”

While astronomers have always been fascinated by the features of the universe millions of light-years away, the physicists at IceCube have shown that looking deep into Earth offers a better way to understand the universe in areas where conventional methods fail. 

Written by: Naren Krishna Jegan — science@theaggie.org