Helgoland Rovelli, Erica (cat reading book .TXT) 📖

Picasso—the influential style of painting that was shaped in Europe in the same years that quantum theory was developing. Cubism and quantum theory both moved away from the idea that the world is representable from a single perspective. In the first decades of the twentieth century, it is the whole of European culture that no longer thinks we can represent the world in a simple and complete way. The anthropologist Claude Lévi-Strauss understands that to study a culture is to change it; Sigmund Freud understands that doctors cannot evaluate patients’ minds without affecting them. In Italy, between the years 1909 and 1925, the years during which quantum theory is born, Luigi Pirandello writes One, No One and One Hundred Thousand (1926), which speaks of the splintering of reality into the points of view of countless observers . . .

QBism abandons a realistic image of the world, beyond what we can see or measure. The theory gives us the probability that we will see something, and this is all that it is legitimate to say. It is not legitimate to say anything about the cat or the photon when we are not actually observing them.

QBism holds a drastically instrumental conception of science: the theory gives predictions only about what a subject can see. I think that science is not just about making predictions. It also provides us with a vision of reality, a conceptual framework for thinking about things. It is this aspiration that has made scientific thought so effective. If the objective of science was solely to make predictions, Copernicus would not have discovered anything new with respect to Ptolemy. His astronomical predictions are no better than Ptolemy’s. But Copernicus found a key with which to rethink everything, to reach a new level of understanding.

The weakness of QBism, in my opinion—and this is the turning point in this whole discussion—is that QBism anchors reality to a subject of knowledge, an “I” that knows, as if it stood outside nature. Instead of seeing the observer as a part of the world, QBism sees the world reflected in the observer. In so doing, it leaves behind naive materialism but ends up falling into an implicit form of idealism.51 The crucial point that QBism disregards, I believe, is that the observer himself can be observed. We have no reason to doubt that every real observer is himself described by quantum theory.

If I observe an observer, I see things that the observer does not. I deduce, by reasonable analogy, that therefore there are also things that I, as an observer, do not see. I want a theory of physics that accounts for the structure of the universe, that clarifies what it is to be an observer in the universe, not a theory that makes the universe depend on me observing it.

In the end, all of the interpretations of quantum theory outlined in this chapter repeat the debate between Schrödinger and Heisenberg: between a “wave mechanics” that tries at all costs to avoid indeterminacy and probability in the world, and the radical leap of the “boys’ physics” that seems to depend too much upon the existence of a subject who “observes.” This chapter has introduced us to an array of intriguing ideas, but it has not allowed us to make a real step forward.

Who is the subject who knows and retains information? What is the information that the subject has? What is, after all, this subject who observes? Does it escape from the laws of nature, or is it subjected to and described by natural laws? If it is part of nature, why treat it as in any way special?

This question, one of countless reformulations of the central question raised by Heisenberg—what is an observation? what is an observer?—finally brings us to the main concept of this book: relations.

III

IS IT POSSIBLE THAT SOMETHING IS REAL IN RELATION TO YOU BUT NOT IN RELATION TO ME?

Where I finally talk about relations.

THERE WAS A TIME WHEN THE WORLD SEEMED SIMPLE

At the time Dante was writing, in Europe we thought of the world as the blurred mirror of a great celestial hierarchy: a great God and His spheres of angels carried the planets in their course across the heavens and participated with trepidation and love in the lives of a fragile humanity which oscillated, at the center of the universe, between adoration, rebellion and guilt.

Then our views changed. In the centuries that followed, we understood aspects of reality, discovered hidden grammars, found strategies for our objectives. Scientific thinking has woven a complex edifice of knowledge. Physics has played a determining and unifying role, providing a clear image of reality: a vast space where particles run, pushed and pulled by forces. Faraday and Maxwell added the electromagnetic “field”: an entity diffused in space through which distant bodies exercise influence upon each other. Einstein completed the picture by showing that gravity is also carried by a “field”: a field that is the very geometry of space and time. The synthesis is tremendously lucid and beautiful.

Reality is a luxuriant stratification: snow-covered mountains and forests, the smiles of friends, the rumble of the subway on dirty winter mornings, our insatiable thirst, the dance of our fingers across a laptop keyboard, the taste of bread, the sorrow of the world, the night sky, the immensity of the stars, Venus shining alone in the ultramarine blue of twilight . . . Behind this disordered veil of appearances, we thought we had found the deep weave, the hidden order. This was the time in which things seemed simple.

But the great hopes of the insignificant mortal critters that we are too often turn out to be short-lived dreams. The conceptual clarity of classical physics has been swept away by quanta. Reality is decidedly not how it is described by classical physics.

This was an abrupt awakening from the pleasant sleep in which we had been cradled by