Antarctica and neutrinos are our best shot at understanding something extraordinary: quantum gravity

Theoretical physicists have been toying around with the idea of ​​unifying general relativity and quantum mechanics for just over a century. Practically from the same moment that the two branches of physics saw the light at the beginning of the twentieth century. The problem is Match the description Things both very big and very small are never easy. In fact, if it weren't so difficult, theoretical physicists would probably have already achieved their goal.

String theory and loop quantum gravity are the quantum theories that most support gravity, although it is not worth overlooking the existence of a post-quantum theory of classical gravity proposed by Jonathan Oppenheim, a professor of quantum theory at University College London. . Scientists realize how important it is to reconcile these two physics theories, and achieving this involves expanding our knowledge about the way subatomic particles interact with the space-time continuum.

The problem is that the mass of the particles is very small and their interaction with space-time is very weak, making measuring this last parameter very difficult. Luckily, Neutrinos are here to save us. In fact, these elusive particles are the real heroes of this article. Without them, physicists at the Niels Bohr Institute Embedded at the University of Copenhagen (Denmark) would not have been able to carry out the experiment they designed to put a face and eyes on quantum gravity.

Neutrinos and quantum gravity face to face

Neutrinos are the most elusive particles in nature. They were first described in the 1930s by Wolfgang Pauli, one of the fathers of quantum physics (to whom we owe, among other contributions, what is known as… Exclusion principle). However, their experimental discovery occurred two and a half decades later, in the mid-1950s. There is a compelling reason why these particles exist. It is very difficult to detect: They barely interact with ordinary matter.

Its mass is very small, its electrical charge is neutral, and it is not affected by the strong nuclear interaction or the electromagnetic force, although it is affected by gravity and the weak nuclear interaction. There is no doubt about that They are very special molecules. Scientists often explain how difficult it is to capture neutrinos by explaining that every second several trillion of these particles pass through the Earth and through us without colliding with any other particles.

The scientists at the Niels Bohr Institute, whom I mentioned a few lines above, have designed a very ingenious experiment using the facilities of the Ice Cube Neutrino Observatory in Antarctica, at Amundsen-Scott. Their goal is, as they themselves explain in the interesting article they published in it Nature physicsAnd analyze the behavior of a large number of neutrinos of atmospheric origin to study the structure of the space-time continuum and test the basic principles of quantum mechanics. No more, no less.

In general, what they did was analyze the interaction of neutrinos in the energy range spanning 0.5 to 10 TeV and the space-time continuum to determine whether they are particles or not. Suffering from a loss of cohesion During its spread. In order not to overly complicate this article, we can assume that coherence loss occurs when the fundamental configuration of the neutrino changes as a result, in this case, of its interaction with space-time. In reality, this process is a bit more complicated, but this description helps us understand what we are talking about.

After carefully analyzing the data collected by the Ice Cube Observatory, physicists at the Niels Bohr Institute came to the conclusion that they did not find any evidence of the emergence of an anomalous decoherence process that would reveal the possible interaction between neutrinos and quantum gravity. However, this does not mean at all that the latter does not exist. In fact, this experiment supports the possibility of determining quantum gravity using this strategy.

The next step requires analyzing this same interaction, but using neutrinos that originate deep in the universe rather than neutrinos found in the atmosphere. It is possible that by resorting to these neutrinos and Using more accurate detectors Finally, it is possible to identify its interaction with quantum gravity, if it actually occurs. Whatever the case, we will find ourselves in another exciting chapter of physics. The one whose arrival will keep us waiting.

Image | As Michelle67

More information | Nature physics

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