Scientists have searched for a “new spatio-temporal structure” under the South Pole. That’s what they found

Scientists have been peering into the structure of spacetime to search for new physics that could be written in the signatures of elusive ‘ghost particles’, with the help of a gigantic observatory that spans nearly a mile under the South Pole, reports a new study.

Although this years-long experiment found no new physics imprinted in these spectral particles, known as neutrinos, it still represents an unprecedented glimpse into the dark realms of the cosmos that have remained out of sight until now. In particular, the new research sheds light on the quest to describe gravity using quantum mechanics, as this so-called “quantum gravity” holds a major key to unlocking some of the universe’s greatest mysteries.

The IceCube Neutrino Observatory, the world’s largest neutrino telescope, has been operating at the South Pole for a decade. The detector is made up of thousands of sensors that reach some 2,500 meters below the ice of Antarctica, about the length of 28 football fields, where they capture energetic neutrinos that come from explosive events at the edges of time and space.

Now, the IceCube collaboration, a team that includes more than 400 scientists, has announced the results of a “search for a new space-time structure” that probed regions of the universe that were previously “unreachable by technological human, according to a study published on Monday in Natural Physics.

“IceCube is really special because it can see neutrinos coming from very far away and with very high energy,” said Teppei Katori, a member of the IceCube team and an experimental particle physicist at King’s College London, as well as a co-author of the study, during a call with Motherboard.

“We use these two properties; that neutrinos can travel the longest distance in the universe and at the highest energy,” he continued. “It’s a big guess, but these particles are thought to be very sensitive to anything in spacetime.”

Neutrinos are so light that their masses are almost imperceptible, earning them the nickname “ghost particles”. Because of this, they are able to effortlessly traverse planets, stars, and other forms of matter without slowing down or changing direction. This makes neutrinos very difficult to detect with conventional instruments, even though they are so abundant in the universe that around 100 trillion of them pass through your body every second.

Most neutrinos around the Earth are thrown by the Sun, but there is another class of high-energy “astrophysical neutrinos” that come from pyrotechnic objects called “cosmic accelerators” located several billion light-years from the Sun. Earth. These accelerators could be objects such as blazars, which are galactic centers that shoot out jets of light and energy, although the exact sources of astrophysical neutrinos are still unknown.

Neutrinos come in three different “flavors” which are associated with fundamental particles of the universe called electrons, muons and taus. Scientists have long suspected that changes in the flavor of astrophysical neutrinos could open a window into regions of spacetime that could challenge so-called Lorentz symmetry, which is an important foundation of the theory of Albert Einstein’s special relativity.

Lorentz symmetry basically means that the cosmos should look the same for two observers moving at a constant speed relative to each other. In other words, the large-scale universe is fundamentally isotropic and homogeneous, even though it appears more varied on smaller scales, including the planetary perspective we experience as humans on Earth. Researchers are obsessed with detecting violations of this symmetry because they could reveal the long-sought missing link between gravity and the standard model of particle physics that governs quantum mechanics.

“For the past 100 years, people have been trying to find evidence that Lorentz symmetry isn’t true, and no one can find it,” Katori explained. “It’s one of the most traditional studies in modern physics – people are questioning this theory of space-time.”

“If something is wrong with Lorentz symmetry or something is beyond Lorentz symmetry, you might have a connection, for the first time, with gravity in the Standard Model,” he said. he adds. “Quantum gravity is something that a lot of people are hoping to be really next-gen, or a doorway to the next step.”

Astrophysical neutrinos offer a promising test of Einstein’s theories because they could encounter unexplored regions of spacetime that are affected by quantum gravity. Neutrinos passing through such areas could potentially change flavor in surprising ways, leaving a record of spacetime anomalies in their signatures that could be read by scientists capturing them on Earth.

“Neutrinos change flavor even without this spacetime effect,” Katori noted. “We look for abnormal changes or unforeseen ways to change. This is the subject of this research.

IceCube’s research found no anomalies in the flavor conversion of neutrinos, leaving the notion of Lorentz symmetry intact for now. Although Katori said these results were somewhat “disappointing” – who wouldn’t want to discover new physics, after all? – this remains an important discovery. IceCube was able to “unambiguously reach the parameter space of quantum gravity-driven physics,” according to the study. In other words, the results have opened a new path in the theoretical field of quantum gravity that will have all kinds of applications for scientists in all fields.

“We think these are great results,” Katori said. “We have the highest sensitivity and we are also the first experiment to reach a region – or ‘phase space’, the technical word – to really search for it,” referring to violations of Lorentz symmetry.

“I’m so relieved that it’s finally being released,” he continued. “Of data taking and other issues, it’s just such a long effort.”

Even as this first experiment draws to a bittersweet end, a new beginning is emerging beneath the ice of Antarctica, along with other instruments around the world. The IceCube collaboration plans to run through its dataset again using new machine learning techniques that may be able to identify anomalies that were missed in this study. The team also hopes to significantly increase the size of IceCube in order to obtain an even larger dataset that could finally reveal traces of spacetime anomalies that point to quantum gravity.

“In my opinion, there is still a chance,” Katori said. “This analysis is the first iteration of its kind. We made it into an analysis framework and developed the code, but in a way we didn’t make the best of the best because things are still in development.

“I believe there is a chance to improve it,” he noted, “but I can’t guarantee how much.”

In the meantime, the new results show that it’s possible to probe spacetime itself using gliding particles from the distant universe, offering a way to explore a host of other potential models and experiments.

“Although the motivation for this analysis is to seek evidence for quantum gravity, the formalism we used is model-independent, and our results may set limits for various new models of physics, including a novel long-term force range, neutrino-dark energy coupling, neutrino-dark matter scattering, violation of the equivalence principle, etc.,” the IceCube collaboration concluded in the study.