Reality Is Not What It Seems: The Journey to Quantum Gravity

by Carlo Rovelli

For him the world is not made of things; it’s constituted of an abstract mathematical structure that shows us how things appear, and how they behave when manifesting themselves.

It’s a magical encounter between logic and intuition.

Dirac’s quantum mechanics is the mathematical theory used today by any engineer, chemist, or molecular biologist.

In it, every object is defined by an abstract space,* and has no property in itself, apart from those that are unchanging, such as mass. Its position and velocity, its angular momentum and its electrical potential only acquire reality when it collides—interacts—with another object.

This is literal independence

The relational aspect of the theory becomes universal.

Dirac provides the general recipe to compute the set of values that a physical variable can take.* These values are analogous to the spectra of the light emitted by atoms. Today we call the set of the particular values that a variable may assume—the “spectrum” of that variable, by analogy with the “spectra” into which the light of elements decomposes—the first manifestation of this phenomenon.

The theory also gives information on which value of the spectrum will manifest itself in the next interaction, but only in the form of probabilities. We do not know with certainty where the electron will appear, but we can compute the probability that it will appear here or there.

This is a radical change from Newton’s theory, where it is possible, in principle, to predict the future with certainty. Quantum mechanics brings probability to the heart of the evolution of things. This indeterminacy is the third cornerstone of quantum mechanics: the discovery that chance operates at the atomic level.

This is also how a thought process manifests in brain chemistry? This exchanging of electrons?

While Newton’s physics allows for the prediction of the future with exactitude, if we have sufficient information about the initial data and if we can make the calculations, quantum mechanics allows us to calculate only the probability of an event.

This absence of determinism at small scale is int...

An electron is not obliged by nature to move toward the right or the left...

Is this due to baked in duality of the positive and negative spins of the electromagnetic spectrum... Is breath our autonomic electron exchanger - the actual breath of life.

The apparent determinism of the macroscopic world is due only to the fact that the microscopic randomness cancels out on average, leaving only fluctuations too...

Dirac’s quantum mechanics thus allows us to...

First, to calculate which values a physical vari...

This is called “calculation of the spectrum of a variable”; it captures the gr...

This is Dirac’s quantum mechanics: a recipe for calculating the spectra of the variables, and a recipe for calculating the probability that one or another value in the spectrum appears during an interaction.

What happens between one interaction and the next is not mentioned in the theory.

It does not...

Well, take the equation of quantum mechanics that determines the form of the orbitals of an electron. This equation has a certain number of solutions, and these solutions correspond exactly to: hydrogen, helium, oxygen . . . and the other elements!

Shortly after completing the general formulation of quantum mechanics, Dirac realizes that the theory can be directly applied to fields such as the electromagnetic one and can be made consistent with special relativity.

(Making it consistent with general relativity will prove much harder and is the main subject of this book.)

The notions of fields and particles, separated by Faraday and Maxwell, end up merging in quantum mechanics.

the equation of Dirac determines the values a variable can take. Applied to the energy of Faraday’s lines, they tell us that this energy can take on only certain values and not others.

Since the energy of the electromagnetic field can take on only certain values, the field behaves like a set of packets of energy. These are precisely the quanta of energy introduced by Planck and Einstein thirty ye...

The electromagnetic waves are vibrations of Faraday’s lines, but also, at small scale, swarms of photons.

Photons are the “quanta” of the electromagnetic field.

“quantum field” similar to Faraday and Maxwell’s, subject to granularity and to quantum probability.

The general form of quantum theory compatible with special relativity is thus called “quantum field theory,” and forms the basis of today’s particle physics. Particles are quanta of a field, just as photons are quanta of light. All fields display a granular structure in their interactions.

During the course of the twentieth century, the list of fundamental fields was repeatedly updated, and today we have a theory called the “Standard Model” of elementary particles, which describes almost all we see, with the exception of gravity, in the context of quantum field theory.

The Standard Model is completed by the 1970s.

There are approximately fifteen fields, whose quanta are the elementary particles (electrons, quarks, muons, neutrinos, Higgs, and little else), plus a few fields similar to the electromagnetic one, which describe electromagnetic force and the other forces operating at a nuclear scale, whose quanta are similar to the photons.

This is the strong and weak neuclear forces, possibly a metaphor for realative and absolute truth... Or Einstein's special and general theories of relativity?

Quantum mechanics, with its fields/particles, offers today a spectacularly effective description of nature. The world is not made up of fields and particles but of a single type of entity: the quantum field.

There are no longer particles that move in space with the passage of time, but quantum fields whose elementary events happen in spacetime. The world is strange but simple (figure 4.5). Figure 4.5 What is the world made of?

I think that quantum mechanics has revealed three aspects of the nature of things: granularity, indeterminacy, and the relational structure of the world.

The Holy Trinity... The Three Jewels of Buddhism... 3D... Why does color and sound have the same electromagnetic frequency? Makes me curious, if consistent meditation practice, would allow for one's ability to 'see' more of the spectrum?

The granularity of matter and light is at the heart of quantum theory.

This goes for everything in general.*

Therefore,

What is an orthoganl quantum state?

the first meaning of quantum mechanics is the existence of a limit to the information that can exist within a system: a limit to the number of distin...

This limitation upon infinity, this granularity of nature glimpsed by Democritus, is the first c...

Planck’s constant h measures the elementary scale of ...

The world is a sequence of granular quantum events.

These are discrete, granular, and individual; they are individual interactions of one physical system with another.

An electron, a quantum of a field, a photon, does not follow a trajectory in space but appears in a given place and at a given tim...

Quantum mechanics introduces an elementary indeterminacy to the...

The future is genuinely unpredictable. This is the second fundamental lesson learned with quantum mechanics.

So what is the past? Is the PAST our Karma?

Quantum mechanics reveals to us that the more we look at the detail of the world, the less constant it is.

The world is not made up of tiny pebbles. It is a world of vibrations, a continuous fluctuation, a microscopic swarming of fleeting microevents. The atomism of antiquity had anticipated also this aspect of modern physics: the appearance of laws of probability at a deep level.

The same randomness, the same appearance of probability at an elementary level, is the second key discovery about the world that quantum mechanics expresses.

This technique for computing the probability of a quantum event is called “Feynman’s sum over paths,” and we shall see that it plays a role in quantum gravity.

QUANTA 3: REALITY IS RELATIONAL