THE ORIGINS OF QUANTUM PHYSICS

The phenomenon of magnetism has been known for a very, very long time, since before the advent of capitalism, or even the Middle Ages, before feudalism or the development of aristocracies.

The word magnetism evokes many things for us in these postmodern times we live in. There are those, for example, who perform New Age therapies with magnets, and perhaps some of us still think of that German doctor whose last name was Mesmer. Not to mention “coaching.” But there is yet another perspective that tends to bring the concept closer to us. The development of technology over the past century would have been impossible without magnetism, and technology would be impossible without science. It is this scientific perspective that we sometimes fail to consider. In the case of magnetism, let us remember that it is seldom found alone: it tends to go hand in hand with electricity. In physics, magnetism is a result of the existence of a magnetic field, just as electricity is that of an electric field. Since they are so often found together, however, we generally speak of electromagnetic fields.

Without the existence of this bipartite field, it would be difficult to live: it’s as simple as that. Take light, for example. It doesn’t matter whether it’s red, green, or white: it’s always an electromagnetic field. We are also familiar with electric fields functioning alone, as on those dry days when we find ourselves giving “shocks” to other people. Magnetism, moreover, is what helps us keep the fridge door closed (there is a magnet in the strip of plastic that runs around the frame of the door).

Without an understanding of magnetism, it would be impossible to build a television, or to have perfected its functioning, from cathode ray tubes to LED screens. Neither would we have computers, nor the cellular telephones that allow us to send messages, listen to music… or date online.

Physicists have been studying magnetism and electricity throughout the ages, but it was in the nineteenth century that the greatest progress was made. This was due mainly to two British scientists: Michael Faraday and James C. Maxwell. They were able to bring together the findings of other researchers and contribute new ones of their own, ordering them and synthesizing them into the four laws, known as Maxwell’s equations, according to which the entire theory of electromagnetism is now studied.

Thus, in the nineteenth century, there was already a scientific basis for describing electromagnetic fields and for using their properties to develop technology.

Toward the end of the nineteenth century, however, something happened: an experiment that failed to fit the theory. Questions arose; doubts were kindled. Everything was reviewed, the experiment was redone, all the details were carefully monitored, and the results came out the same. Proposals were made to modify the theory: some aspects were improved, while others were thrown out. Option after option was considered, but nothing quite fit.

It was the colors that were responsible. As simple as that, right? Green, orange, brown, purple, white, violet, yellow, blue, vermilion, fuchsia… And what about black? The only truly guilty party was a blackbody. This was what had left the scientists unable to understand what was happening. It was known that, if a body is illuminated with white light, it appears as yellow to our sight, because only the light of that color is reflected, whereas all the rest is absorbed. The same thing happens if we illuminate a blue object. We see that a bottle of red wine is green because only the green light is reflected to our sight, while the other colors are absorbed. But what happens if we have a blackbody? What is a blackbody in physics? Imagine a sphere, of iron perhaps, that has been hollowed out so that only the shell remains. If we pierce a hole in it and then heat it, we will see that the sphere turns red, like a burning coal or a needle placed in a fire.1 In other words, it emits light (it radiates). The hole allows us to observe what is happening inside, because of the radiation that comes out. Since the cavity also emits light, we can see what there is inside. Could a star be conceived as a sort of blackbody?

Max Planck took a little step further. Just a little step, but one that overturned everything, explained everything, determined, mathematized, revolutionized, conceptualized, and founded everything: indeed, it founded quantum physics. For that little step, Planck was awarded the Nobel Prize in 1918, “in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta.”2

Humanity had not realized the existence of this phenomenon because it happens only in the “micro-world,” in the world of things we cannot see with our eyes, of phenomena that do not appear in everyday life. The term quantum generates curiosity, a premonition of boredom, and even a great deal of extravagant nonsense, spoken as it is with the penetrating gaze of the savant, in an atmosphere of genius, applied to many things beyond its true scope.

But the quantization of energy is as if there were only squares of chocolate of exactly 500 calories. As if we could eat one square, or two, but never leave half of one, or a third, or any little bit of one. We could also eat ten, but only if we’re sure ingest them entirely, however cloying or unhealthy that may be! And the same applies to the production of the squares of chocolate: only whole squares could be produced in the factory, with no possibility of producing packages of half-squares. If the packaging says 500 calories, that’s what it has to be. In the end, a hundred squares might come out of the machine, or 261, or 593, or

D. Halliday, R. Resnick, and K. S. Krane, Physics, vol. 2 (John Wiley and Sons, 2002).

<https://www.nobelprize.org/prizes/physics/1918/summary/>

José Luis Romero Ibarra

graduated with a PhD in physics from the Universidad de Guadalajara. He did post-doctoral work at the KTH Royal Institute of Technology in Sweden, and has held research fellowships in Concepción, Chile, and Rostock, Germany. In the course of his academic career, he has taught mechanics, electromagnetism, and quantum physics, among other subjects.