Italian theoretical physicist, founder of the theory of loop quantum gravity, Carlo Rovelli, in his book called "Helgoland", tries to explain the insanely complex theory of quantum mechanics, considering the world of photons, electrons, atoms and molecules, which obeys rules that run counter to our everyday physical reality. Recall that quantum theory arose from the observations of Heisenberg and Einstein's earlier theory of relativity. Before Einstein, scientists believed in a predictable, deterministic universe governed by a clockwork mechanism. Thus, the Newtonian idea of the absolute "true time", inexorably ticking in the Universe, was opposed by Einstein's theory that there is no single "now", rather, there is a multitude of "now". Heisenberg and his followers believed that we cannot know the current state of the world in every detail. All we are allowed to do is explore the world using uncertainty and probability models.
"The mystery of quantum theory may ultimately be beyond our rough understanding on Earth. But Newtonian mechanics, while far from obsolete, can no longer explain every aspect of the world we live in," Rovelli writes.
Quantum reality
Quantum theory invites us to see the world as a giant cat cradle of relationships, where objects exist only in terms of how they interact with each other. Rovelli believes that Heisenberg's theory is a theory of how things "affect" each other. It forms the backbone of all modern technologies - from computers to nuclear power, lasers, transistors and MRI scanners.
In his inventions, the Italian physicist applies quantum theory to various philosophies. People exist because of their continuous interaction with each other; the same thing happens with atoms and electrons.
Carlo Rovelli at a lecture in Rome / © Marco Tambara / Wikipedia
So, let's take an electron that is emitted at point A and is found at point B. One could assume that the electron follows a trajectory (like a car from point A to point B), but to explain experimental observations, Heisenberg rejected the concept of an electron's trajectory. And the resulting quantum theory deals with probabilities and allows you to calculate the probability of finding an electron at point B.
At the same time, we do not know anything about the path along which the electron moves. In its strictest form, quantum theory completely denies any reality of the electron until it is discovered (leading some to argue that a conscious observer somehow creates reality).
Hidden reality
Since the 1950s, scientists have tried to bring quantum theory into line with the requirements of classical physics, including defending a "hidden" reality in which an electron does indeed have a trajectory, or assuming that an electron travels all possible paths, but these paths appear in different worlds … But Rovelli rejects these attempts.
Instead, in his new book (Helgoland), the physicist explains the "relational" interpretation, in which an electron, say, has properties only when it interacts with something else. When an electron does not interact, it is devoid of physical properties: no position, no speed, no trajectory.
Even more radical is Rovelli's assertion that the properties of an electron are real only for the object with which it interacts, and not for other objects. “The world is splitting into many points of view that do not allow for an unambiguous global vision,” writes Rovelli.
As the Financial Times writes, Quantum physics cannot be made perfectly clear, but Rovelli is excellent at providing as much clarity as possible.
The expectation that objects will have their own independent existence - independent of us and any other objects - is in fact a deep-rooted assumption we make about the world. This assumption has its origins in the scientific revolution of the 17th century and is part of what we call the mechanistic worldview. According to this point of view, the world is like a giant clockwork, the parts of which are governed by the established laws of movement - Carlo Rovelli, "Helgoland".
Object interactions and space-time
So, if we consider space and time as the sum of distances and durations between all objects and events in the world and remove the contents of the Universe from the equation, then we will automatically “remove” both space and time. This is a "relational" view of space-time: they are only spatial and temporal relationships between objects and events. The relational view of space and time was a key source of inspiration for Einstein when he developed general relativity.
Our understanding of space-time can hardly be called complete.
Rovelli uses this idea to understand quantum mechanics. He argues that objects of quantum theory, such as a photon, electron or other fundamental particle, are nothing more than the properties that they exhibit when interacting with other objects - in relation to them. These properties of a quantum object are determined by experiment and include things like the object's position, momentum, and energy. Together they make up the state of the object.
According to Rovelli's relational interpretation, these properties are all that an object has, which means there is no underlying individual substance that "has" properties.
How to understand quantum theory?
In his article for The Conversation, Rovelli offers a look at the well-known quantum puzzle of Schrödinger's cat. We put the cat in a box with some lethal substance (for example, a bottle of poisonous gas), triggered by a quantum process (for example, the decay of a radioactive atom), and close the lid.
A quantum process is a random event. It is impossible to predict it, but we can describe what happened in such a way as to determine the different chances of an atom decaying or its absence within a certain period of time. Since opening the box we will release gas from the bottle, therefore, the death of the cat and her life are also a purely random event.
According to quantum theory, a cat is neither dead nor alive until we open the box and observe the system. It remains a mystery how the cat would feel if it were neither alive nor dead.
But according to the relational interpretation, the state of any system is always in relation to some other system. Thus, a quantum process in a box may have an indefinite result in relation to us, but a definite result for a cat.
So it is quite reasonable that a cat is neither alive nor dead for us, but at the same time it can be dead and alive. For us in this whole story, one fact is real and one fact is real for a cat. When we open the box, the state of the cat becomes certain for us, but the cat has never been in an uncertain state for itself. In the relational interpretation of the global, "Divine" view of reality, e exists. But what, then, does this tell us about the nature of reality?
Most likely, we will never know the answer to the question of what quantum reality is. But it's worth trying.
Rovelli argues that since our world is ultimately quantum, it is worth paying attention to its similar perception. In particular, such objects as, for example, a favorite book, can have their properties only in relation to other objects, including you. Fortunately, this also includes all other items, such as a smartphone or kitchen cabinet. But despite its apparent simplicity, such a view of the world is a dramatic rethinking of the nature of reality.
From this point of view, the world is a complex web of interconnections, so that objects no longer have their own individual existence, independent of other objects, like the endless game of quantum mirrors. Moreover, it is quite possible that at the heart of this network there is no independent "metaphysical" substance that constitutes our reality, writes Rovelli.
So it is possible (as Rovelli himself put it) that the surrounding reality, including ourselves, is nothing more than a thin and fragile veil, behind which … there is nothing. And if we add to this the riddle of the nature of consciousness, then everything becomes even more complicated.