Explaining the inexplicable: can physics be disclosed?

Explaining the inexplicable: can physics be disclosed?
Richard P. Feynman (1918-1988). (DP)

The scientist has a vast experience of ignorance, of doubt, of uncertainty, and such an experience is of the greatest importance. We have discovered that in order to progress it is essential to know how to recognize our ignorance and leave room for doubt. physical

(Richard P. Feynman, ‘The value of science’)

The title of this article could be that of a long conversation I had with the astrophysicist Juan Perez Mercader in the late eighties. I was trying to convince him to write a book for a popular science collection that he was directing at the time, and he, although he liked the idea, didn’t see it entirely clearly. they had just left brief history of timeof Stephen Hawkingy The Emperor’s New Mindof Roger Penrose, two books as interesting as they were out of the reach of the non-specialist public, and I thought that Mercader, a skilful and entertaining communicator, could have dealt with the same topics in a more accessible way; but he doubted that certain fundamental aspects of modern physics could be divulged1. Despite this, he ended up sketching a book project that we worked on for a while, albeit moving very slowly; so slowly that I would end up thinking that Juan’s skepticism was justified and it would take him ten years to finish his book2.

Einstein’s grandmother

They are attributed to Einstein two analogous phrases that refer to one of the basic questions of the theory of knowledge. The sentences are: “If I can’t explain it to my grandmother, I don’t understand it” and “If I can’t draw it, I don’t understand it.” And the question to which they refer is: what does it mean to understand? According to the first of the sentences, understanding something would imply being able to express it colloquially. It is not enough to know the formula E = mc2 and know that E is energy, m mass and c the speed of light; You have to understand (and it’s not easy), in order to explain it to Einstein’s grandmother, that matter can be converted into energy, since matter and energy are two states of the same thing. According to the second sentence, comprehension would be linked to imagination in the most literal sense of the term: the ability to produce significant images that allow visualizing the content of a verbal or alphanumeric statement.

At least in theory, any scientific concept could be explained to Einstein’s hypothetical grandmother in simple words, although the explainer would have to know what was explained very well and have the necessary time to be able to translate into colloquial language, through long circumlocutions, which specialized jargon expresses synthetically and precisely. However, not everything is drawable, not even in a vaguely approximate way. We cannot draw something that is both a particle and a wave, and the well-known representation of the atom as a miniature solar system confuses more than it clarifies. That is why Einstein, a disciple of Spinoza and of Schopenhauercould never accept quantum mechanics, despite being one of its founders.

One of the great paradoxes of science is that the most effective and accurate physical theory ever formulated, the one that best adheres to observed facts and produces the most accurate predictions, is totally counter-intuitive, inherently incomprehensible.3. We can imagine Einstein trying to explain to her grandmother the paradox of Schrödinger’s cat, and her exclaiming: “Don’t talk nonsense, Albert, how can a cat be alive and dead at the same time?” It may have been such an objection that led him to search in vain for thirty years for “hidden variables” that would allow him to draw physics and reconcile with his grandmother.

Dare not to know

In biology, a fundamental book can be both a popular work and even a book. bestseller; is the case of chance and necessityof Jacques Monodo The selfish geneof Richard Dawkins. But in physics such a hybridization does not seem possible. The aforementioned books by Hawking and Penrose (some other equally famous and important ones could be added, such as The quark and the jaguarof Murray Gell-Mann) son bestsellersbut, paradoxically, they are not popular books: a reader without a solid knowledge of physics and mathematics will only understand the introductory chapters, and after confidently advancing through the first pages, he will hopelessly sink into a sea of ​​unintelligible formulas and concepts, as in those beaches where you walk for a few meters and suddenly there is a sharp drop in level that prevents those who do not know how to swim from continuing.

Does this mean that we have to give up spreading modern physics? Quite the contrary, since disseminating is, to a large extent, making clear the limits of knowledge, the frontiers of science, the hesitations and frustrations of those who venture into the unknown. Which is especially important in the case of physics and requires not only great narrative expertise, but also great doses of humility. to the horacian sapere hears we should add a contrasting and complementary dare not know: Dare not to know and to admit that you don’t know. The first thing that a book popularizing modern physics should make clear is that physicists themselves do not fully understand it.

Six not so easy pieces

“If I had to choose a single book to pass on to the next generation of scientists, it would have to be six easy pieces», affirms the prestigious science writer John Gribbin. And surely the book Richard Feynman it is the best introduction to modern physics that can be achieved with hardly any use of jargon or higher mathematics; but even so, the title is deceptively encouraging: the pieces are only comparatively easy, and Feynman himself warns in the first chapter:

You may wonder why we can’t teach physics by simply stating the basic laws on page one and then showing how they apply in all possible circumstances, just like we do with Euclidean geometry, where we state the axioms and then make all sorts of deductions. We cannot do it this way for two reasons. The first is that we do not yet know all the basic laws: the border between knowledge and ignorance is constantly expanding. And the second is that the correct statement of the laws of physics involves some unfamiliar ideas that require advanced mathematics to describe. Therefore, a considerable amount of preparatory training is necessary even to understand what the words mean.

The mind-matter problem

Going straight to the relationship between mind and matter may seem like a sudden jump, but it is not so much: this old philosophical problem, which in its current scientific approach is usually designated, more specifically, as the mind-brain problem , is one of the questions that, in recent decades, has most intrigued some leading physicists, mathematicians and computer scientists, such as Alan Turing, Marvin Minsky, Hans Moravec, Douglas Hofstadter or the aforementioned Roger Penrose. And one of the reasons, although not the only one, for such interest is the relationship of the mind-matter problem with artificial intelligence, perhaps the most important scientific and technological enterprise of all time. And, in turn, the mind-matter problem and the debate on artificial intelligence are inseparable from the so-called “hard problem of consciousness” (hard problem of consciousness), relating to the how and why of qualia, the subjective qualities of individual experiences.

Coincidentally (or perhaps not), while preparing this article I came across a recently published book that addresses the issue from the triple perspective of physics, computer science, and neuroscience: I am me: analyzing the mystery of consciousnessof Jaime Escutia (Autograph, 2023). The author is a physicist and an expert in operating systems, which has allowed him to write an excellent introduction to three closely interconnected key topics: the digital revolution, the new physics (which is already getting old), and the conundrum of consciousness. A highly recommended book for both beginners and laymen. And although the latter will have to bypass the complex formulas that inevitably punctuate some of the passages, they will be able, at least, to get an idea of ​​the magnitude and wonder of what is probably the greatest challenge that human beings have faced in his desire to understand the world and —in a dizzying self-referential loop— his own ability to understand.


(1) “Modern physics” is understood as that after the revolutionary incorporation, at the beginning of the 20th century, of relativity and quantum mechanics.

(2) After several updates, he published it under the title What do we know about the universe? From before the Big Bang to the origin of life (Editorial Debate, 2000).

(3) On one occasion, a disciple of Planck told him that he was beginning to understand quantum mechanics, and Planck replied: “If you think you understand it, you don’t understand it”, and Bohr used to say something similar.


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