Strange Neutrinos That Sparked 'Parallel Universe' Claims Could Be Explained by Dense Snow

In May, headlines appeared saying scientists may have identified a parallel universe where time runs backwards. They had not. The suggestion was based on anomalies recorded at a South Pole research station, where scientists appeared to observe neutrinos coming out of the ground—something that could not be explained.

Neutrinos are subatomic particles that are one of the most abundant in the universe. They are similar to electrons, but have no electrical charge. They also have a very small mass and have little interaction with matter, making them difficult to detect. Neutrinos are constantly bombarding Earth, passing right through the planet unimpeded. It is estimated 100 trillion neutrinos pass through the human body every second.

To understand neutrinos, experiments are taking place at the South Pole. One of these, the Antarctic Impulsive Transient Antenna (ANITA), uses a balloon with radio antennas that track cosmic rays and neutrinos coming from space. In 2016 and 2018, anomalies were found in data from ANITA. Scientists found radio signals that appeared to show high energy neutrinos coming up from the ground.

This could not be explained, with different hypotheses being put forward, from dark matter to sterile neutrinos—hypothetical particles thought only to interact via gravity. Some also suggested it may be evidence of some entirely unknown physics. In 2018, a study was published that discussed the potential of a parallel universe, which was later taken out of context in relation to these findings.

In a paper published in the journal Annals of Glaciology, researchers led by Ian Shoemaker, assistant professor in the Department of Physics and the Center for Neutrino Physics at Virginia Tech, have now put forward another possible explanation.

"I was dismayed at the headlines about a parallel universe in connection with the ANITA events," he told Newsweek. "I would be as excited as anyone if these events were ultimately understood to come from something as exciting as a parallel universe. However, it's probably among the least likely interpretations, especially given that we may not need new physics at all to explain the events."

In the paper, the team say densely packed snow, known as firn, may be responsible. Firn is not quite dense enough to be ice, meaning you can have areas beneath the surface with wide ranging densities. The unusual recordings could be reflections of high energy cosmic rays.

"The strangest thing about the ANITA events is that they appear to be coming from neutrinos that have two properties that don't usually go together: extremely high energies and directions indicating that they came up through the Earth," Shoemaker said.

"The reason these two features don't usually go together is that neutrinos interact very strongly with matter at high energies, so much so that the Earth itself should effectively absorb neutrinos. In other words, with conventional physics it is challenging to reconcile the energy and direction of these events."

He said the most likely explanation of these anomalies is that they are not coming up from out of the ground and they are not neutrino events. Other events from space can also produce radio waves that can be picked up by the ANITA experiment, he said. Shoemaker and colleagues suggest cosmic ray radio signals could reflect off subsurface features beneath the surface of the ice and create a "fake neutrino event." Properties beneath the ice could explain the unusual events.

Image depicting Antarctica from space. Experiments are taking place at the South Pole to detect neutrinos. iStock

"These features could be tested directly with direct radio survey of the regions in the vicinity of the ANITA events, so the hypothesis is quite testable," he said.

Peter Gorham, physics and astronomy University of Hawaii, who works on ANITA but was not involved in the latest study, told Newsweek he was not convinced of the findings.

He said subsurface layers were something they had considered during the original analysis of the anomalies. He said the researchers find that under "possible, favorable" conditions, a reflection may occur and while this cannot be excluded, "such simulations are critical to matching observations."

"Our observations, especially those from the second event, show a very coherent, clean radio impulse with no evidence of distortion," Gorham said. "Within our collaboration, we have extensively simulated subsurface reflectors using full-wave optics and we find that such subsurface reflectors never lead to clean and coherent signals, there is always distortion of some portion of the radio band. So our conclusions lead us to believe that subsurface reflectors are not yet a plausible explanation for our observations."