Beauty will describe the world

by Michele Di Ego

In Dostoevsky’s “The Idiot”, Prince Myškin is asked if it is true that he said that beauty will save the world. The phrase, thanks to its poetry, ended up having even greater fame than the novel itself. Whether or not beauty will save the world, I cannot say; however, as a physicist I can ascertain that it helps to describe it.

If it is true that the ultimate goal of physics is to be able to describe the world in mathematical laws that find confirmation in experiments, and therefore to get as close as possible to a rational and unequivocal truth, it is also true that scientific research is always carried out by man, which by definition is imperfect. Physics is greater and more perfect than the man who creates it. And although in physics a term with imprecise outlines like “beauty” does not have a place, for physicists the concept of beauty can become fundamental. Physicists rely on beauty for guidance in their endeavour to discover the truth.

The universe is therefore a malleable object, in which distances and time are shortened and broaden under the effect of the presence and movements of masses.

They immediately understand when an equation, a theory, a discovery is beautiful, elegant and simple.

Abstract ideas aside, to bring on some concrete examples, the Nobel Prize winner Murray Gell Mann in 1957 decided to publish an article concerning weak interactions (the forces responsible for the decay of atoms). Despite the fact that there were seven experiments which refuted his theory, he was convinced that his idea had been so clean and elegant it could not have been wrong and suggested that it was the experiments that had been poorly performed. He was right.

Moreover: all nuclear and subnuclear physics is based on the correspondence of symmetric particles with specular characteristics. To understand what we are talking about, let’s start by saying that any object around us is composed of atoms. A single atom is composed of an electrically positive nucleus around which electrically negative electrons orbit. The nucleus is divided into protons and neutrons. Both protons and neutrons are in turn composed of quarks. There are three pairs of quarks (up/down, strange/charm, truth/beauty). Going back to electrons, they belong to a category of three pairs of particles called leptons (electron, muon and tau, paired to their three neutrinos). All the matter known to us in the universe can be described in terms of three pairs of quarks and three pairs of leptons.

In the 1970s, there was a discrepancy between the number of known pairs of quarks (which at the time were two) and the number of known pairs of leptons (three). This absence of symmetry made physicists believe that there must also be a third pair of quarks. Eventually the experiments proved them right and after years the two missing quarks were found.

Generally, in physics, revolutionary discoveries tend to include previous notions in a new theory capable of unifying what until then seemed irreconcilable, through laws that appear more elegant and complete.

Let’s start with Greek philosopher Aristotle. He had noticed that any object, in order to remain in motion, needed a force that would push it, otherwise it would come to rest sooner or later. Galileo takes a step forward, realizing that what happens is actually the opposite: the friction that stops a moving body is the manifestation of a force, and in the absence of braking forces a moving body would remain in perpetual motion. The objects then communicate with each other through forces which cause them to deviate in motion. The next step is entrusted to Newton who says exactly how these deviations take place: the forces modify the motion of the bodies making them accelerate with an acceleration inversely proportional to their mass (the famous F=ma). Not only that: there is a force which acts without contact between bodies: gravity. And the force of gravity, which keeps us with our feet on the ground or makes apples fall from trees, is the exact same force that acts between the moon and the Earth, or between the Earth and the Sun: the law of gravitation is therefore universal. This is the crucial step: from the apple to the moon, the unification between earthly mechanics and celestial mechanics.

After Newton it is Einstein who deals with gravity, starting from the intuition that nothing can move faster than light. We all know that light from our Sun takes about eight minutes to reach Earth. If we could instantly make the Sun disappear into thin air, we would then have eight more minutes before darkness engulfs us. What about gravity? After how long would the Earth stop following its elliptical orbit, dictated by the attraction exerted by the Sun? Newton would have replied that in the very moment of the disappearance of the Sun, Earth would have deviated from its trajectory to proceed in a straight line. But Einstein did not agree, for the German scientist nothing is faster than light and therefore not even gravity: Earth would continue undaunted to orbit for eight minutes around a Sun that has now disappeared.

From these premises Einstein is able to conceive a new model of the universe, in which space and time are not absolute and rigid, but are continuously deformed by the presence of matter and energy. For a moving body, the structure of time slows down: the faster the body goes, the more time slows down. An example? Muons are formed by the impact of cosmic rays with the highest layers of the atmosphere and, before decaying, they “live” a few millionths of a second. Which means that they shouldn’t be able to reach Earth’s surface, being too far away for them. Why is it possible for us to measure their presence here too? Because, approaching the speed of light, the structure of time slows down for them, allowing them to “live” longer and reach us. But it is not necessary to travel at the speed of light to expand time: every moving body changes its time; even we as we walk, but our speed is so small compared to that of light that the effects on us are completely negligible. Potentially, if we had a sufficiently precise watch, we might be able to observe the time expansion of any moving body. A real experiment is the following. Two atomic clocks are synchronized. The first is placed on a plane, while the second is left on the ground. The plane takes off, travels a certain route at high speed and then lands. At this point the two clocks are compared: they are no longer synchronized, the time has passed differently for them.

But Einstein’s predictions go far beyond the cited-previously examples. Not only does speed change the temporal and spatial structure: the mass itself of a body is able to modify it. The closer we are to a mass, the slower is time for us. If we could get close to a huge mass, like a black hole, time for us would slow down tremendously and a minute for us would correspond to years (or centuries) on Earth – it is on this phenomenon that the movie “Interstellar” is entirely based.

The universe is therefore a malleable object, in which distances and time are shortened and broaden under the effect of the presence and movements of masses.

But the focal point is the following: Einstein’s theory of relativity includes Newton’s gravitation, showing how the latter is a good approximation, valid for explaining a number of phenomena (such as the apple on Earth or the Earth’s orbit around the Sun), but not sufficient to explain others (such as the presence of muons at ground level or time dilation phenomena).

Today it is known that there are four fundamental forces (gravitational, strong force – which keeps the nuclei of atoms glued together, the previously named weak force and the electromagnetic force). The new great revolution that could modify our conception of the universe would see the unification of these four forces, showing us how they are nothing but different sides of the same coin. This theory goes under the name of “theory of everything”, and at the moment we are still far from being able to see it first-hand.

But the attempt itself by physicists to unify the fundamental forces stems from the awareness that, historically, apparently different phenomena have proven to belong to a higher law that was able to unite them. And this awareness does not arise from a written rule of physics, it is a promise in which physicists believe inwardly, without being able to give a formal explanation.

Somehow physics embraces Keats’s suggestion: “Beauty is truth, truth beauty”.