The Science Behind the Neutrino Observatory Awarded the Nobel Prize in Physics

At a depth of 1.6 kilometers beneath the surface in the state of South Dakota, USA, giant caves are being prepared that are intended to help answer one of humanity's oldest questions—how the universe originated. Access to these caves is provided by an elevator that transports scientists into the Earth's depths.

Researchers from Project Dune have demonstrated the route to an underground laboratory built for one of the world's most ambitious scientific experiments. These installations are located in the city of Lead and will be equipped with particle detectors capable of revealing the secrets of the origin and evolution of the universe. Among the technologies used is equipment developed by the University of Campinas (Unicamp).

This report is part of the 'Unicamp 60' series produced by EPTV to celebrate the sixtieth anniversary of the University of Campinas. EPTV 2 broadcasts a series of five episodes demonstrating how the university contributes to Brazil's development through research and life stories.

Why is the laboratory located so deep underground?

Scientists are studying underground caves at a depth of 1.6 km in South Dakota, USA, where Project Dune neutrino detectors will be installed. These caves were excavated to house detectors that will analyze neutrinos—subatomic particles so difficult to observe that they are called 'ghost particles.'

Neutrinos, formed naturally in phenomena such as solar nuclear reactions, pass through planets, rocks, and even the human body with almost no interaction with matter. The lab's depth is critical because it blocks most of the cosmic radiation reaching the surface, thereby reducing interference during measurements.

The experiment will proceed as follows: a particle accelerator at Fermilab, a laboratory near Chicago, will create a beam of neutrinos. These particles will then travel approximately 1300 kilometers through the Earth to South Dakota. The final stage involves giant detectors filled with liquid argon registering rare moments of neutrino interaction with matter.

Cave excavation work was completed in August 2024, and the main focus is now on installing the equipment for the experiment.

What is the role of Unicamp?

Brazilian participation is crucial for the functioning of the detectors. Researchers led by Unicamp have developed two technologies that will be used in the underground laboratory.

The first technology is a liquid argon purification system designed to remove impurities that could jeopardize the results. Each of the four planned detectors will contain about 17 thousand tons of this substance. Physicist Pascoal Pagliuso, coordinator of research at the university, explained: 'Researchers from Brazil, led by Unicamp, managed to develop an innovative methodology for purifying liquid argon to remove oxygen and nitrogen.'

The second technology is X-Arapuca, a device that captures light signals generated when neutrinos interact with argon. Since such interactions are extremely rare, collecting the maximum amount of information is vital for the study. According to physicist Ana Amélia Bergamini Machado from Unicamp, the signals recorded by the sensors allow for measuring particle properties, such as their energy.

In addition to Unicamp, specialists from several other institutions are involved in the project, including the Federal University of São Carlos (UFSCar), the University of São Paulo (USP) in São Carlos, the Federal University of São João del Rei (UFSJ), the Federal University of Alfenas (Unifal), the Federal University of ABC (UFABC), the Aeronautical Technology Institute (ITA), the Federal Technological University of Paraná (UTFPR), the Brazilian Center for Physical Research (CBPF), the National Center for Energy and Materials Research (CNPEM), the Renato Archer Information Technology Center (CTI), and the University of Liverpool in the UK.

The total investment in the mega-project amounts to approximately 20 billion Brazilian reais, with Brazil's share estimated at around 200 million reais, funded by the State of São Paulo Research Support Fund (Fapesp) and the Finep Financing Agency.

What do scientists hope to discover?

Dune, which means 'Deep Underground Neutrino Experiment' in English, unites over 200 institutions from at least 35 countries and aims to understand the properties of neutrinos that currently challenge the foundations of physics.

One of the main questions is why matter prevailed over antimatter after the Big Bang, which allowed stars, planets, and ultimately life to form. Pagliuso noted: 'The community's most accepted model for the origin of the universe is the Big Bang. But how it happened and how it evolved to the state the universe exists in today remains a very big mystery.'

Scientists also plan to study neutrinos generated by stellar explosions, which could provide insights into the formation of neutron stars and black holes. Researchers predict that the detectors will be able to begin studying naturally occurring neutrinos even before the full operation of the Fermilab beam.

According to Pagliuso, the project seeks answers that go far beyond particle physics. He added: 'When we think about the universe in a playful way, we want to understand who we are, where we came from, and where we are going.'

Scientists from the Japanese space agency JAXA have discovered signs of an underground tunnel approximately 50 kilometers long in the Marius Hills region of the Moon. This information was obtained after analyzing radar data collected by the Kaguya orbital spacecraft. Researchers believe that if this tunnel exists, it could potentially be used in the future for human habitation on the Moon.

The Moon lacks an atmosphere and the weather conditions characteristic of Earth. There is a risk from harmful cosmic rays, small meteorites, and sharp temperature fluctuations. An underground tunnel could provide protection against these threats. However, complete information about this tunnel is currently unknown, and it remains to be determined how safe it would be for humans to reside inside.

In 2009, the Kaguya orbital spacecraft captured images of the Moon, which showed a large crater in the Marius Hills area named Marius Hills Hall. This crater was estimated to be about 50 meters wide and 50 meters deep. This section of the Moon is visible from Earth. Scientists suspected that this crater might be an opening to a large underground tunnel, leading them to check radar data for large voids beneath the lunar surface.

The Kaguya orbital spacecraft was equipped with the Lunar Radar Sounder (LRS), which directed radar signals toward the Moon's surface. These signals reflected back, helping scientists understand the subsurface structure. In 2017, an article published in the journal Geophysical Research Letters described signals indicating the probability of large underground cavities. Based on this data, the hypothesis of a lava tube approximately 50 kilometers long was proposed. Nevertheless, due to radar limitations, every part of the tunnel could not be inspected, necessitating further research to confirm its full length and structure.

According to scientists, volcanic eruptions occurred on the Moon a very long time ago, spewing out hot lava. When the lava stopped flowing, its outer layer cooled and solidified, while the hotter inner lava continued to move forward, forming a long, tunnel-like space underground. Such structures are called lava tubes. The Marius Hills region contains numerous structures formed by volcanic activity. Scientists hypothesize that this tunnel may be around 3.5 billion years old, and studying it could help better understand the ancient history of the Moon.

A safe zone is critically important for long-term human presence on the Moon. It is difficult to protect against harmful cosmic rays and small meteorites. An underground tunnel could offer protection from these factors and also mitigate the impact of sharp temperature changes. Scientists hope that signs of water or ice might be found in such locations, but there is currently no confirmation of water or ice within this tunnel. Now, scientists must determine the size of the tunnel and the strength of its ceiling and walls. Only then can it be decided whether this location is suitable for human settlement. If future research confirms these assumptions, this tunnel could become a refuge for people on the Moon in the future. For now, this discovery represents an important step in understanding the Moon's subterranean spaces.