Carlo Rovelli is an important theoretical physicist and popularizer. Its main scientific activity is within the theory of quantum severity to loop (Loop Quantum Gravity), of which it is one of the founders. Among his volumes we mention seven short physics lessons, international bestseller translated into 41 languages and Helgoland (both Adelphi) precisely dedicated to the birth of quantum mechanics and on the island in the North Sea where, in June 1925, one hundred years ago, the German physicist Werner Heisenberg began to elaborate his theory. Nobody more suitable for talking about the centenary of quantum mechanics.
Professor Rovelli, let’s start from the beginning. Because there is quantum mechanics, there must be the concept of “how much” that if I remember correctly it was postulated by Max Planck at the stroke of the 1900s. Can you explain it to it in a simple way?
«Max Planck in 1900 made a calculation that reproduced well certain laboratory measures, but of which he himself was the first not to understand the meaning. It was Albert Einstein, in 1905 who introduced the concept of what. The simplest words to explain it are his, in the opening of the 1905 article: it seems to me that phenomena connected with the emission and transformation of light are better understandable if it is assumed that the energy of light is distributed in space in a discontinuous way. Here I consider the hypothesis that the energy of a radius of light is not distributed continuously in space, but it consists instead in a finite number of how many energy that are located in points of the space, move without dividing themselves and are produced and absorbed as single units. This is the birth of the quantities: of concentrated energy packages ».
In quantum mechanics, the wave-particle dualism thinks … it is complex. It can leave us a bit like a cat closed in a box … disoriented.
«I think we are wrong to think that there is a wave. The wave lies only in our calculations. The wave is only a way to say that the particles move in a somewhat random and jumping way ».
In the previous question I quoted, laterally, the famous mental experiment of Schrödinger’s cat.
It is the scientist who is most linked to quantum. But in the same years many genius scientists have worked there: from Heisenberg to Born …
«Erwin Schrödinger contributed importantly, but when he wrote his works the quantum mechanics already existed, practically complete, in the works of Max Born, Werner Heisenberg, Paul Dirac, and Pascual Jordan. These are the real heroes who have solved the problem first ».
Why at a certain point all the physics that counts is having to deal with how many?
«Because it is not only electrons and photons that behave in a quantum. Everything behaves quantumly. Everything evolves in a probabilistic way, jumps, and everything is granular as light. Even if for big things you often see less. Quantum mechanics today is used to study atoms, molecules, materials, molecular biology, computers, laser, stars and the evolution of the universe “.
Even the time looked at quantumly we no longer recognize it. Not only does it become relative but almost point. Can you help us understand this with an example too?
«Quantum mechanics has been applied with great success to all physical systems, less one. What is missing is the gravitational field. There are preliminary theories, but we are not yet safe are right, like quantum severity at loop. I work on this. In light of these theories, we expect even the time to be made of those who are not really continuous, but consist of very small elementary timing. A far from recent idea, moreover, already existed in ancient Islamic philosophy “.
The layman has the impression of dealing with two physicists. A macroscopic that works on the basis of classic physics and a microscopic that follows different rules. In the end these two physicists somehow come together?
“They are already united. The things we have not studied well seem to us always mysterious and disconnected from what we already know. But they are not, on closer inspection ».
She worked a lot for a quantum theory of gravity. Why is it important?
«Because we are curious to discover something about what we still don’t know. If we don’t know what happened in the primordial universe, or what happens inside black holes, it is because we have not yet understood the quantum properties of space and time well ».
Could you take us to a theory of everything?
«I hope not and I think not. To me the theories completely always seem only pious illusions. We are very far from knowing everything ».
Speaking of gravity, is it inevitable to touch the theory of strings … can you summarize in a simple concept?
«It is an attempt to write a theory that has collected a lot of enthusiasm in past years, but has not produced what was at the beginning hoped, and went to disappointments when she tried to look for support by making verifiable predictions. Today it appears to most scientists less promising than in the past ».
Oppenheimer seems to have said to his students: “I can repire it ten times but I can’t make it easier than it is …”. But if most people do not understand a certain type of physics …
“Most people, including me, wouldn’t know
reconstruct a radio. But it has always been like this. Civilization is the beautiful thing that happens when everyone contributes in one part, each understands a piece of the general matter, we trust each other, and we collaborate ».