Quantum Theory & Reality

Quantum Theory & Reality

The meaning of quantum theory is quite easy to understand, but it is so jarring to our natural presuppositions it has lain undiscovered all this time. It means there are two different kinds of real physical world. This idea is well-established in modern physics. What is new is the realisation that both are real operational attributes of the physical reality one encounters as a conscious individual.

At the theoretical level the two different types of world is a well-understood concept. As Lev Vaidman describes:

A world is the totality of macroscopic objects: stars, cities, people, grains of sand, etc. in a definite classically described state. This definition is based on the common attitude to the concept of world shared by human beings. Another concept (considered in some approaches as the basic one, e.g., in Saunders 1995) is a relative, or perspectival, world … a centered world. This concept is useful when a world is centered on a perceptual state of a sentient being. In this world, all objects which the sentient being perceives have definite states, but objects that are not under observation might be in a superposition of different (classical) states. (2014)

The difficulties in understanding the new physics arise because the world on which we do experiments is a relative, centred world, and thus gives results incomprehensible when applied to the ordinary type of world, technically a ‘quasi-classical’ world. As shown here both types of world are real. They exist and operate at different ‘levels of logical type’.

This section of the site goes into the physics of quantum theory to explain where all this comes from and what the technical implications are.

The Quantum

Here’s what we know for sure. Quantum theory defines physical reality at the most fundamental level. Everything is made of quanta. An electron is a quantum of matter. The movement of electrons is what we know as electricity. A photon is a quantum of energy in the form of light. The problem is that the quanta work in a quite different kind of way to how the world works at the ordinary everyday level. It is so different that despite a hundred years of research it is still not clear exactly how the real world is actually defined. As stated by Wayne Myrvold:

Despite its status as a core part of contemporary physics, there is no consensus among physicists or philosophers of physics on the question of what, if anything, the empirical success of quantum theory is telling us about the physical world. (2016)

Wave-Particle Duality

The whole thing is summed up as ‘wave-particle duality‘. A quantum is defined by a ‘wave function‘, which is a wave of probability. Below is an illustration of the spreading wave function of a single quantum coming through two very narrow slits at the top of the diagram.

The wave function of a single quantum passing through two slits.

Then, the moment it is observed it becomes a tiny real thing. The wave collapses to produce a submicroscopic ‘point particle’, such as an electron in a specific location. Everything not observed stays as a wave of probability, essentially unreal. That is the standard textbook explanation in a nutshell. This is the basis of the ‘Copenhagen interpretation‘ that emerged in the 1920s.

So there is a strange dualism of two different types of existence, particle and wave. The great paradox is that this means physical reality operates two different and incompatible ‘dynamics’, rules of operation. This is described in detail in The Measurement Problem.

The Dynamics

The world we are familiar with operates according to Newton’s three laws of motion, which he discovered three hundred years ago. This is the dynamics of what is now called ‘classical physics‘. We have a direct intuitive grasp of these rules of operation. This is how we know how to catch a ball and throw it accurately. It means that the world is an objectively real domain of matter and energy, all working like clockwork.

The dynamics of classical physics is the one we are used to. Our mental processes and our bodily capabilities have been tuned in to this dynamics since birth. We now know how this type of world emerges from the quantum realm. The operation of the huge number of quanta that go to make up any ordinary everyday object average out exactly to give rise to the laws of classical physics.

The Dualism

Quantum theory shows us there are two different dynamics. The ‘linear dynamics’ is the fundamental way the quantum operates, as defined by the wave function. This determines the way an electron will change position as time progresses. It is the ‘linear dynamics’ of all the quanta that sum to form the ordinary world.

As you can see from the image above, in the linear dynamics the future position becomes more and more spread out as time progresses. But the moment it is observed the wave function collapses to a tiny sub-atomic particle. This is the ‘collapse dynamics’. This is a total mystery, hence the measurement problem. How this happens, why this happens and even whether it does in fact happen have been deep mysteries for a hundred years.

Many Worlds

The Copenhagen interpretation in the 1920s held that collapse is a real physical phenomenon. The other possibilities just do not come to be. But this does not stack up. In 1957 Hugh Everett presented a solution to all the problems. This is the famous ‘many-worlds’ theory. Everett simply takes the physics at face value. There is no collapse, which means that all the possibilities actually happen. In this case the linear dynamics gives rise to all possible worlds, hence the name of the theory. That was far too strange to be even considered at the time and the whole thing was automatically rejected. But nowadays it is increasingly accepted. An excellent article that includes a description of this progression is 100 Years of Quantum Mysteries written by John Wheeler and Max Tegmark.


Even more difficult to imagine, these worlds are all here and now. As Brian Cox states, the many worlds are really just one world of superposed mishmash:

There is only one ‘world’, and it is a world in which everything that can happen does happen and everything is in a superposition with everything else. (2017)

So the universe we live in is all possible worlds all at once, a superposition of real worlds.

The superposition of real solid stuff sounds rather crazy but this principle is fundamental to quantum mechanics. In fact the superposition principle is perfectly logical, given what we know. At the fundamental level all physical matter and energy is defined by wave functions. And wave functions simply define the probabilities of events, interactions of matter and energy. So it is just adding together probabilities.

So down at the quantum level worlds are made of wave functions, and so they add together like waves on water. This is the illustration of waves adding together from the Wikipedia page on the superposition principle. This principle will come in very important later on in resolving the great paradoxes.

Ducks on water where interference of ripples is visible

The Appearance of Collapse

Everett’s explanation resolves all the problems, but it is so strange that the crucial aspect of his theory has never been accepted. Firstly, it means that all possible versions of events happen, which is how all possible worlds come into being. This is increasingly accepted in modern physics. The big question is why we observe only one outcome when we do experiments, when all possible outcomes are real in this universe. Everett’s brilliant solution is that there is no actual collapse. There is just the appearance of collapse, to the observer. But this is where all the trouble lies with understanding what he really means.

This great illustration is gratis Max Tegmark. When Bob asks Alice out for a drink, objectively both outcomes must happen. So here we see the two different outcomes, happening in separate realities that branch and go their separate ways. This is what Everett says happens, but only in experience.


Quatum cartoon by Max Tegmark of reality dividing at a choice point: Gratis Max Tegmark.

So this is different to objective physical reality. Objectively, from a birds eye view, both situations exist superposed as Cox describes.

Second version of quantum cartoon in which the two versions of reality are superposed

So objectively the world is actually like this second picture. But in experience, subjectively, the world works like the first picture. That is Everett’s theory – the ‘Relative State’ formulation of quantum mechanics. The trouble is no one can understand it. How can the experience be different from the real physical world in which the observer exists?

The State of the Memory

Everett holds that it all seems simple enough. As he describes, with regard to the observer as a physical entity, when an observation is made the result:

… is a superposition of states, each element of which assigns a different state to the memory of the observer. (1957, 462)


Judged by the state of the memory (1957, 462)

is there just one specific version of the event observed. So the branching diagram is an illustration of what happens in experience, while the physical reality is all superposed. In what follows we will see how this comes to be.

It is because of the nature of the subject of the reality, which is widely acknowledged as lacking definition in the quantum theory, the ‘observer’. For this we need to understand exactly what he means by the state of the memory.


The nature of the state of the memory is something so familiar and intrinsic to us that the technical description sounds a bit odd. This is the perceptual reality. And the perceptual reality is a virtual reality.

The state of the memory is defined as the record of observations. Each observation is a three-dimensional construct. From the signals generated by the eyes, the brain constructs a three-dimensional rendering of the environment that is perceived. And each such observation is recorded in memory. It sounds as if it is just information in the brain, but it is so very much more significant than this suggests.

The World Hologram

The integrated synthesis of the record of these observations forms the complete definition of the perceptual reality. As described by Dawkins and Deutsch quoted in The World Hologram, this is a virtual reality.

This virtual-reality representation is mapped perfectly onto the real world that is actually there. That is its purpose. This is the navigation system of the human organism. In other words, the reality you are experiencing directly is the spatially-distributed representation of the world, mentally projected onto the world. This is the amazing natural technology of the brain that enables us to perceive the world and interact with it. This is the operation of the navigation equipment of the human observer.

The form of the perceptual reality is a holographic field of information that is mentally projected onto the real world, so as to match up precisely with the three-dimensional physical reality. I call it the world hologram.

The Inside View

Nonetheless, this is just something in the brain of the observer, so how can this have a different physical reality to the body in which it exists? How could just this information have the strange kind of material significance that Everett proposes? The answer is that this is the ‘inside view’ of the universe.

As Tegmark describes, in physics it is crucial that we distinguish between two different types of frame of reference:

• the outside view of the world (the way a mathematician thinks of it, i.e., as an evolving wavefunction), and
• the inside view, the way it is perceived from the subjective … perspective of an observer in it.
(1997, 2)

The outside view is the objective view on which all physics is based. It is sometimes called the ‘view from nowhere’. The world hologram is literally the inside view of course, the way the world is perceived by an observer. The nature of this domain is elaborated in The Inside View.

The difference between the two views is that on the outside view all possibilities happen, but on the inside view only one version of reality is experienced. This is what Everett is saying. As we shall see, the world of the inside view is the different type of world, a centred world.

The Superworld

The centred world is a weird idea. Why would a whole world be defined just by the observations made by the observer. The ‘superworld’ is the new idea presented here that makes sense of the centred world. As Tegmark describes in his articles, there are many identical copies of you in the many-worlds universe. This means that your world hologram exists in a great many worlds. And these worlds are all superposed, as Cox describes. And that means that the physical reality on this inside view is superposition of all these worlds. It is a ‘class-of-worlds-as-a-world’.

It has one very special property, determinate only where observed, by definition. All the worlds are the same where observed. So the sum of them all is determinate and real, where observed. But everywhere else it is indeterminate because that is the sum of all possible versions of everything else, all superposed.

This type of world is here called a ‘world superposition’, ‘superworld’ for short. This is the reason there are two different types of world. The superworld is a ‘second-logical-type’ phenomenon. The technical details are given in The Superworld.

Effective Collapse

It is this type of world that naturally resolves the great puzzle of collapse. The mechanism is quite simple. The making of an observation is the addition of that sensory data to the record of observations. This addition alters the state of the world hologram. And this means that the world hologram exists in a different version of the world, a version where the observed event has determinately happened. Effectively the collapse dynamics operates because the definition of the superworld changes.

After the experience of Alice saying yes, the world hologram of a delighted Bob exists in a different superworld, the class of all the worlds in which she said yes. And in a parallel version he lives in a different superworld, the superposition of all the no worlds. It is the superworld that branches into two different versions.

And all the physics works perfectly. This is described in detail in The Superworld. This provides the explanation of the relative, centred world Vaidman describes, the ontology.


This is also the world defined in the latest interpretation of quantum theory, Quantum Bayesianism, now shortened to QBism. As the authors show, the world is indeterminate except where observed by a specific observer. And all else remains indeterminate. As they demonstrate this:

… removes the paradoxes, conundra, and pseudo-problems that have plagued quantum foundations for the past nine decades. (Fuchs et al., 2013, 1)

But it is not taken seriously, let alone accepted because there is no ontology, no explanation in terms of fundamental existence. The superworld is the ontology. The inside view is the view of a superworld, and it works exactly as described in QBism. A full explanation is given in QBism.

Dualism Explained

The evidence is clear to see once we know what we are looking at. It is this type of world, a superworld, on which all physics experiments are in fact performed. When we do experiments we observe collapse in action because this is the inevitable effect in the centred world, the world defined by observations.

It seems like a paradox because it looks as if we are just experimenting on the objective physical reality of the quasi-classical world. And of course it must look like this, by definition. This is the superposition of the class of worlds that look exactly the same, on this inside view.

So there are two different types of physical world, the ordinary quasi-classical world and the relative, centred world, the superworld. This is the explanation of the dualism of incompatible dynamics of the measurement problem. They operate in the two different types of world. The linear dynamics is the dynamics of a quasi-classical world. This operates at the first, primitive level of logical type. The collapse dynamics is the dynamics of a superworld. This operates at the second level of logical type because it is the phenomenon of a whole class of worlds. This is all described in The Superworld.

The New View

As described in The World Hologram, this field of information is the active subject of the dynamics. This is the protagonist Everett describes for which the collapse dynamics is a real phenomenon. This is the ‘observer’. This is the key piece missing from the current picture in modern physics. The quotes are used because the observer is inevitably taken to be a physical entity.

So as the operational conscious individual you are the world hologram, and you live in a superworld. The experimental evidence for the new perspective is given in The Holographic Universe. The really exciting thing is that this kind of world is not only personal, it is a domain in which the individual is at cause in a remarkable manner, as described in Interactive Destiny. This is the basis of the new worldview that liberates us from being just passive bystanders in the affairs of the world. There is a strange new responsibility, but also a radical new empowerment.