– Artyom Valeryanovich, the Royal Swedish Academy of Sciences has just announced the award of the Nobel Prize in Physics to two scientists – Arthur McDonald of Canada and Takaaki Kajita of Japan – for the discovery of neutrino oscillations. What do you think about it?
– I think it is a truly great discovery. Let me try to explain why it matters, starting from a distance. Why do you think the stars, the Sun included, shine? Because thermonuclear reactions take place in them, turning hydrogen into helium.
We have never flown to the stars; we cannot test this experimentally. There is simply no other explanation for why the stars shine.
And if thermonuclear reactions take place in the stars, they must be accompanied by the emission of a certain number of neutrinos. I should note that these are very fast particles that barely interact with anything. They practically don't interact at all. A neutrino can pass right through the Earth without, as they say, noticing.
For that reason scientists were unable to catch neutrinos for a long time. But when they learned how to do it, it turned out that there were very few of these particles. So few that some physicists began to doubt that thermonuclear reactions take place in the stars at all. A serious scandal was brewing in scientific circles. But the discovery of neutrino oscillations averted it.
The thing is, there are three types of neutrino – electron, muon and tau. When solar neutrinos were analysed, only electron neutrinos were taken into account. And then it turned out that one kind of particle can transform into another. That, in fact, is what neutrino oscillations are. In other words, a star emits enough neutrinos in its thermonuclear reactions; it's just that on the way some particles turn into others. Scientists used to believe such metamorphoses were impossible, because the neutrino has no mass. That would simply contradict the conservation law. But McDonald and Kajita established that neutrino oscillations exist, confirming along the way that the neutrino does have mass, albeit a very small one. And if so, then all is well. Everything has fallen into place.
– In other words, this discovery only confirmed what scientists had suspected before?
– By and large, yes. And it isn't the only scientific discovery of this kind in the last three or four years. Just take the Higgs boson (the existence of this elementary particle, also called the "God particle", was predicted by the English physicist Peter Higgs in 1964, but it was discovered with the help of the hadron collider only in 2013. — author's note). If we hadn't found the Higgs boson, it would have been a great misfortune. It would have meant that our ideas about elementary particle physics and, as a consequence, about string theory and other theories that play a decisive role in cosmology were wrong. Physics is a real science – a single experiment is enough to send the most beautiful theories, built up over years and even decades, into the waste-paper basket. That's why we believe in it!
– So it turns out that scientists first built a huge tower and only then started reinforcing the foundations?
– Not quite… People often underestimate the importance of a good physical theory. Usually, when people say "it's a theory", they mean it's some kind of nonsense. In fact, a meaningful physical theory is completely inseparable from practice. And there is incomparably more sense in it than – forgive the tautology – in our common sense. I don't even know what amazes me more in this world: that we understand almost everything about how the Universe works, or that we have turned out to be capable of building models that allowed us to understand it all.
– You say we understand everything, or almost everything, about the Universe. Doesn't that strike you as a somewhat self-confident claim? Medieval scholars who seriously searched for a way to obtain the philosopher's stone also thought they understood how the world works. And today their ideas about it can only raise a smile…
– No, I don't think so. I can accept that in two or three hundred years a new level of understanding of the Universe will come, and that it will be many times higher than today's. But the models created today, I'm sure, will not make people laugh. Look: when Einstein's theory appeared, it turned out that Newton's theory is a special case of it. When quantum mechanics appeared, it turned out that classical mechanics works only in certain situations – but it works! So the old theories, being correct, were simply incorporated into a broader body of knowledge. That's the first point.
Secondly, we shouldn't look down on the alchemists. It was largely thanks to them that a perfectly meaningful chemistry emerged, once all the mystical nonsense had been discarded.
And thirdly, the knowledge and capabilities at the disposal of modern science really are very great.
I keep trying to get across to people that modern science is more powerful than the magic described in books like Harry Potter (let me say straight away: I like Harry Potter, but that's not the point). In essence, it is already something divine in its power… Tell me, please, where can ordinary matter turn into gold? Only inside stars and in laboratories on Earth. The lowest temperatures are found not in observable space but, again, in our laboratories. If you think about it, the Earth is one of the most unusual places in the Universe. And people today are almost like gods. They just don't realise it.
Isn't it a miracle that I can predict how many stars, on average, will explode in our Galaxy this year? Stars! Isn't it a miracle that on a small planet there lives some barely noticeable "mould" capable of asking itself such questions and, most importantly, of finding the right answers to them?
– In Gorky's novel The Life of Klim Samgin, the character Stepan Tomilin says something to the effect that through man matter strives to know itself…
– Maybe that's how it is. It would be a good explanation of where on earth this astonishing ability of ours to understand how the world works comes from. Man, a finite being, can find out with complete certainty whether the Universe is finite or infinite. Do you know how? It all depends on the density of matter in the Universe. If it is below the critical value, the Universe is infinite; if it equals the critical value, it is also infinite. If it is higher, the Universe is finite. The task comes down simply to measuring that density. We measured it. The mass of matter turned out to be critical. By all appearances, the Universe really is infinite.
– You know, one question has always bothered me in this connection. If the Universe is infinite, then there must be countless worlds similar to ours. Including ones in which, right now, in an identical office, a journalist is talking to the Vice-Rector for Research of the Kant Baltic Federal University.
– By all appearances, that is the case. This paradox is discussed, in particular, in Alex Vilenkin's wonderful book Many Worlds in One. But there is one nuance here. The Universe, as we have established, is infinite. But how many different types of history are possible in it? According to classical theory, based on continuous space and time, the number of such histories is also infinite. In quantum theory everything is different. There, any history requires precise initial conditions. But they cannot be specified more precisely than the Heisenberg uncertainty principle allows. Roughly speaking, when you examine very small regions, you eventually find that you can't tell one thing from another, so you have to identify them all. Hence the conclusion: the number of possible quasi-classical histories is finite. But the Universe is infinite. And that means that at some point histories must repeat. So somewhere in the Universe, at a very great distance from us, on an identical planet Earth, in an identical city of Kaliningrad, at this very moment, two people who are literally identical to us are sitting and talking about the same things as you and I. And somewhere else – also very far away – at some point you get tired of listening to me, so you get up and leave. There are a great many ways events can unfold.
The question may arise: "Does quantum theory apply to human beings?" Well, why not? After all, we are made of atoms, which in turn are made of elementary particles that exist according to the laws of quantum mechanics.
Translated from Russian with the help of AI (Claude, Anthropic), October 2026.
