Scientists are searching for evidence of the existence of quantum gravity in Antarctica

Thousands of sensors spread across square kilometers near the South Pole are on a mission to answer one of the great unanswered questions in physics: Does quantum gravity exist? The sensor monitors neutrinos (particles with no charge and little mass) arriving at Earth from space. A team at the Niels Bohr Institute (NBI) at the University of Copenhagen has helped develop a method that uses neutrino data to reveal whether quantum gravity exists.

“If quantum gravity does indeed exist, as we believe, this would contribute to unifying the two current worlds of physics. Today, classical physics It describes phenomena in a normal environment, but the atomic world can only be explained using quantum mechanics.

“Unifying quantum theory and gravity remains one of the most prominent challenges in fundamental physics, and it would be very satisfying if we could contribute to that goal,” said NBI Assistant Professor Tom Stuttard.

Stuttard is a co-author of a paper published in the journal. natural physics. This article presents the results of a large-scale study by the NBI team and American colleagues. More than 300,000 neutrinos have been studied.

However, these are not the most interesting types of neutrinos that originate from deep space sources. The neutrinos in this study were produced in Earth’s atmosphere by high-energy particles from space colliding with nitrogen and other molecules.

“Observing neutrinos originating from Earth’s atmosphere has the practical advantage of being much more common than other neutrinos originating from space. To validate our methodology, we need to We needed data from neutrinos, and this is now complete. So we’re ready to do the next step in studying neutrinos from deep space,” Stuttard said. he says.

Travel around the world without being disturbed

The IceCube Neutrino Observatory is located next to the Amundsen-Scott South Pole Station in Antarctica. In contrast to most other astronomy and astrophysics facilities, IceCube is ideal for observing the universe on the other side of the Earth, the Northern Hemisphere. This is because neutrinos are capable of completely penetrating our planet, and even its hot, dense core, while other particles are blocked, so neutrinos coming from the northern hemisphere have a much cleaner signal. That’s why.

The IceCube facility is operated by the University of Wisconsin-Madison, USA. More than 300 scientists from around the world participated in the IceCube collaboration. The University of Copenhagen is one of more than 50 universities with her IceCube center for neutrino research.

Because neutrinos have no electric charge and almost no mass, they can travel billions of light-years through space in their original state, unperturbed by electromagnetic or powerful nuclear forces.

An important question is whether the properties of neutrinos actually change at all over long distances, or whether small changes are significant after all.

“If neutrinos undergo the subtle changes we suspect, this would be the first strong evidence for quantum gravity,” Stuttard said.

Neutrinos have three flavors

To understand what changes in neutrino properties the team is looking for, some background information is needed. Although we call it a particle, what we observe as a neutrino is actually three particles produced together, known in quantum mechanics as a superposition.

Neutrinos can have three basic configurations (what physicists call flavors): electrons, muons, and tau. Which of these configurations change as the neutrino moves? This is a really strange phenomenon known as neutrino oscillation. This quantum behavior is maintained over thousands of kilometers and is called quantum coherence.

“In most experiments, coherence breaks quickly. But this is not thought to be caused by quantum gravity. It is just very difficult to create perfect conditions in the lab. necessary, but somehow a few molecules manage to sneak in,” etc.

“In contrast, neutrinos are special in that they are unaffected by the matter around them, so we know that if their coherence breaks down, it is not due to a flaw in the experimental setup.” He explains.

Many colleagues were skeptical

We asked whether the study results were published in 2016. natural physics “We found ourselves in the rare category of scientific projects: experiments for which there was no established theoretical framework. Therefore, we did not know what to expect. But… Some of the general properties we expect a quantum theory of gravity to have.”

“We had hopes that we would see changes related to quantum gravity, but the fact that we didn’t see it doesn’t at all exclude that it’s a reality. Atmospheric neutrinos If it’s detected at an Antarctic facility, it will usually have passed through there.” “This is Earth, which means about 12,700 km, which is a very short distance compared to neutrinos that originate from far away in space.” “Clearly, quantum gravity would require much longer distances to have an effect if it were present,” Stuttard said, adding that the holy grail is: The focus of the research was to establish a methodology.

“For years, many physicists have wondered whether it would be possible to test quantum gravity in experiments. Our analysis shows that it is indeed possible, and astrophysics We hope that future measurements of neutrinos and more accurate detectors built over the next decade will finally answer this fundamental question. ”