A view of the IceCube Neutrino Observatory, which is buried at depths between 1.5 and 2.5 kilometers below the Antarctic ice, at the South Pole. The only visible equipment above the surface is the IceCube Lab, which hosts the computers that collect data from the over 5,000 light sensors in the ice. Credit: IceCube Collaboration/NSF
“If as we believe, quantum gravity does indeed exist, this will contribute to unite the current two worlds in physics. Today, classical physics describes the phenomena in our normal surroundings such as gravity, while the atomic world can only be described using quantum mechanics. The unification of quantum theory and gravitation remains one of the most outstanding challenges in fundamental physics.
The IceCube facility is operated by the University of Wisconsin-Madison, USA. More than 300 scientists from countries around the world are engaged in the IceCube collaboration. University of Copenhagen is one of more than 50 universities having an IceCube center for neutrino studies. “If the neutrino undergoes the subtle changes that we suspect, this would be the first strong evidence of quantum gravity,” says Tom Stuttard.To understand which changes in neutrino properties the team is looking for, some background information is called for. While we refer to it as a particle, what we observe as a neutrino is really three particles produced together, known in quantum mechanics as superposition.
“Whilst we did have hopes of seeing changes related to quantum gravity, the fact that we didn’t see them does not exclude at all that they are real. When an atmospheric neutrino is detected at the Antarctic facility, it will typically have traveled through the Earth. Meaning approximately 12,700 km — a very short distance compared to neutrinos originating in the distant Universe.