Helgoland

In our everyday life we are not aware of any of this. Quantum interference gets lost in the buzz of the macroscopic world. We can reveal it only through delicate observations, isolating objects as much as possible.⁷⁹ To see genuine quantum phenomena clearly we have to isolate things as much as possible.

If we do not observe interference, we can ignore superposition and reinterpret it as ignorance: we just don’t know if the cat is asleep or awake. We have no need to think that there is a quantum superposition because quantum superposition – I emphasize it as there is often confusion on the issue – means only that we see interference. The delicate phenomena of interference between the cat awake and the sleeping cat are lost in the noise of the world that surrounds us. When interference is lost, we can take facts as stable, that is, we can forget that they are only true relative to something else.⁸⁰

Furthermore, when we observe the world at our scale we do not see its granularity. We cannot see single molecules: we see the whole cat. With many variables, fluctuations become irrelevant, and probability nears certainty.⁸¹ Billions of discontinuous events of the agitated and fluctuating quantum world are reduced by us to the few continuous and well-defined variables of our everyday experience. At our scale, the world is like the wave-agitated surface of the ocean seen from the moon: the smooth surface of a blue marble.

Our everyday experience is thus compatible with the quantum world: quantum theory incorporates classical mechanics and our usual vision of the world – as approximations. We understand it as a man with good sight can understand the experience of a myopic person. But at the molecular scale, the cutting edge of a sharp knife is as fluctuating and imprecise as the edge of an ocean in a storm, fraying upon the white sand of its shore.

The solidity of the classical vision of the world is nothing other than our own myopia. The certainties of classical physics are just probabilities. The well-defined and solid picture of the world given by the old physics is an illusion.

The notion of a chair is defined by its function: a piece of furniture designed for us to sit on. It presupposes human beings who sit down. It’s about the way we conceive of it.

This does not affect the fact that the chair exists right here, objectively. The object is still here, with its obvious physical characteristics of colour, hardness, and so on. But even these characteristics exist only in relation to us. Colour comes from the encounter between the frequencies of light reflected from the surfaces of the chair and the particular receptors in human retinas. It is not about the chair: it is a story between light, retina and reflection. Most other animal species do not see colours as we do. The frequencies themselves emitted by the chair emerge only from the interaction between the dynamics of its atoms and the light that illuminates them.

The chair, still, is an object independent of its colour. If I move it, it moves as a whole. Strictly speaking, not even this is completely true: this chair is made of a seat that rests on a frame, which rises when I pick it up. It is a set, an assemblage of pieces.

What is it that makes this assemblage of pieces a single object, a unit? Effectively, it is little more than the role that this combination of elements plays for us...

If we look for the chair in itself, independently of external relations, and especially of its relations to us, we struggle to find it.

There is nothing mysterious about this: the world is not divided into stand-alone entities. It is we who divide it into objects for our convenience. A mountain chain is not divided into individual mountains: it is we who divide it up into parts that strike us as in some way separate. A countless number of our definitions, perhaps all of them, are relational: a mother is a mother because she has a child, a planet is a planet because it orbits a star; a predator is such because it hunts prey; a position in space is there only in relation to something else. Even time exists only as a set of relations.¹²⁵

None of this is new. But physics has long been asked to provide a firm basis on which to place relations: a basic reality underlying and supporting this relational world. Classical physics, with its idea of matter that moves in space, characterised by primary qualities (shape) that come before secondary ones (colour), seemed to be able to play this role: to furnish the primary ingredients of the world that it was possible to think of as existing in their own right, as the basis of the interplay of combinations and relations.

If I look at a forest from afar, I see a dark green velvet. As I move towards it, the velvet breaks up into trunks, branches and leaves: the bark of the trunks, the moss, the insects, the teeming complexity. In every eye of every ladybird there is an extremely elaborate structure of cells, connected to neurons that guide and enable them to live. Every cell is a city, every protein a castle of atoms; in each atomic nucleus an inferno of quantum dynamics is stirring, quarks and gluons swirl, excitations of quantum fields. This is only a small wood on a small planet that revolves around a little star, among one hundred billion stars of one of the thousand billion galaxies constellated with dazzling cosmic events. In every corner of the universe we find vertiginous wells of layers of reality.

In these layers we have been able to recognize regularities, and have gathered information relevant to ourselves that has enabled us to create a picture of each layer and to think about it with a certain coherence. Each one is an approximation. Reality is not divided into levels. The levels into which we break it down, the objects into which it appears to be divided, are the ways in which nature relates to us, in dynamical configurations of physical events in our brain that we call concepts. The separation of reality into levels is relative to our way of being in interaction with it.