Just before the sunset, Man approaches and sits between Carla and Peter at the campfire.
“I noticed that you have visited Ferdinand. How are you today?”, asks Carla to Man.
“After a week I had hoped to get used to the heat during daytime and to feel better, but that does not happen. My health remains worrisome, in a few days I will have to decide if it's necessary to travel to Nairobi and return to Amsterdam by plane”, says Man.
“If this is the case, then I will return with you”, says Carla.
“You should not do that; you should visit the family of Narrator.
Yesterday night, you said – sitting at the campfire – that entropy in our universe can only increase : the order changes – without help and support from the outside – irrevocably in chaos and decay. This applies to a home and car, and I think this also applies to our body, that requires more time and rest for older people to recover from efforts. Now I notice that I don’t recover well from traveling: in past travelling was no burden for me. I wonder, why do we only change from young to old? I would not like to go back in time – in my case from old man via young man to my birth again – like Merlin in "The Once and Future King" by Terence White . There has happened too much in my life: I have had a rich life, rich in joy and rich in sorrow; my personal life has now been completed. But the question remains: why can’t we go back in time; why does our life go from the past to the future; why can’t we live from the future to the past?”, asks Man to Carla.
“In the world of ideal physics – a world without entropy – there is no preference for the direction of time. A capture of two crashing billiard balls on an ideal billiards table can be turned smoothly forward and backward in time without any alienation. The same applies to the exchange of a photon between two electrons. I will draw the Feynman diagram  for this exchange in the sand.
In spacetime diagrams, the progress is rendered from bottom to bottom, just as a cash slip leaves the cash register. But in this Feynman diagram, the course of time can as well unfold in the opposite direction from top to bottom: in that case the arrows on the two electrons on either side of the diagram are reversed, and the photon  – similar to the electromagnetic energy (shown as ? in the diagram) – returns to the other electron and thus reverses in time .
In everyday life, the probability that a process unfolds according to a given time path, is much higher, than that it might unfold in reverse order in time. In analogy with Albert Einstein's “Gedankenexperimenten” or "Thought Experiments"  I will show this by the following thought experiment in two parts.
In the first part of the thought experiment a laser is placed in a dark room. This laser emits every few seconds one photon at a time to one of the eyes of a woman. The emitting of the photons is recorded on a timeline. The woman a button with pushes her finger, when she observes photon with one of her eyes.  The button is connected to a counter that records on a timeline when and how often the woman presses the button. After a certain period of time, the observation timeline by the woman is compared with the timeline of emitted photons by the laser. Suppose 40 percent of the emitted photons are correctly recorded by the woman on the observation timeline – or better said: 40 percent of the registrations on both timelines correspond – and 10 percent of the observed photons have not been transmitted by the laser, but these are recorded wrongly by the woman on the observation timeline. This is a very good outcome of the first part of this part of the thought experiment. The two deviations in the observation of photons can be explained by:
- some part of the emitted photons is absorbed into the eye lens and parts of the retina that cannot detect photons (see illustration below) and
- a random nerve activity delivering a signal that a photon has been observed, while no photon has touched the retina. In addition, with an extremely small chance, an electron in the eye may emit a photon that is detected by the retina. On this last option I will come back later.
In the second part of the thought experiment, the woman is again in the same dark room. She is instructed to randomly transmit one photon every couple of seconds to a sensor that is located two meters away from her. As she sends a photon, she is instructed to push a button that is connected to a counter that records on a timeline when the woman presses the button.
The outcome of this second part is as expected:
- Every now and then the sensor detects the observation of a photon. The timeline of this registration by the sensor does not have any relation with the registration of the moments when the woman presses the button, because she imagines sending a photon with her eyes.
The first part of the thought experiment shows, that the first process of detecting photons by the human eye and at the same time pushing a button unfolds rather well in the course of time. The reverse process in the second part of the thought experiment – wherein the registration of photons emitted by the eye is compared with the "intention of the woman to emit a photon" – unfolds disastrous over time.
Both parts of this thought experiment show that a process unfolds well in our usual direction of time, but outright hopeless in the reverse direction of time.
We humans are focused on survival and we pay attention to processes that are most useful for our survival, while we try to avoid processes that are not useful for our survival. This means that hopeless processes in the reverse course of time do not get any attention because these processes are not important to us.
We arrange the timelines of important processes – such as a day, the gestation period of an animal or a human child, a year cycle, a human life or the existence of humanity – by reference timelines, and thereby we experience the progress of time. The extremely minimal chance of reversing of these familiar processes, we rightly overlook in everyday life. As a result, we do not experience the possibility of an extremely small chance that a process can also be reversed, sporadically, e.g. a group of cells of a person who get younger for a short period of time, and then simply age again.
The astronomer, physicist and mathematician Arthur Eddington  – whom I had mentioned several times in relation to black holes and also as opponent of the Indian astrophysicist Chandrasekhar – described in 1928 in his book "The Nature of the Physical World"  the change over time according to the "Arrow of Time" on the timeline.
Arthur Eddington wrote about this "Arrow of Time", that when we follow the arrow and we get more and more of the random element, then the "Arrow of Time" points to the future. If the random element decreases, then the arrow points to the past. This is the only known difference between future and past in physics. This is immediately clear if the basic theorem is acknowledged that the introduction of randomness – and quantum mechanical irregularities – is the only thing that cannot be undone. Arthur Eddington uses the concept of "Arrow of Time" to express this one-way feature of time that does not occur in space.
After that, Eddington noted three points about the "Arrow of Time":
- The "Arrow of Time" is clearly recognisable with our consciousness;
- The "Arrow of Time" forces itself upon us through our gift for reasoning and judgment, that tells us that a reversal of the arrow of time makes our common world insane;
- The "Arrow of Time" does not occur in physics, except in the study of the organisation of a number of individuals.
According to Arthur Eddington, the "Arrow of Time" indicates the gradual progression/progress of the arbitrary elements. After a long argument about the nature of thermodynamics, he concludes that, as far as physics is concerned, the "Arrow of Time" arises only from a characteristic of entropy.
I am not completely convinced by Arthur Eddington's argumentation, because I think that the "Arrow of Time" is experienced by people in daily life, because a number of processes progress much easier in one direction. In reverse order, these processes have an extremely small chance of manifesting themselves in everyday life. I have tried to demonstrate this by the thought experiment of the perception and transmission of photons by the human eye in. The important changes for human – e.g. aging – consist of many processes that each have a good chance of taking place, and that must subsequently take place in a correct order. If one of these processes goes completely wrong, the person in question will die prematurely.
The chance of a person getting younger, requires many processes after each other, that each have only a very small chance of taking place.
This is the beginning of my answer. Can you still follow it?”, asks Carla.
“I have to think of our gastrointestinal tract, where the normal process goes more or less by itself in the course of time. The reverse road is anything but fun, but a healthy person usually only throws up after eating spoiled food”, says Ferdinand.
“True. Carla, your reasoning resembles a pocket billiards – or pool billiards – where it is easy to spread the triangle of coloured balls in a few seconds by the white ball over the billiard sheet. But it's almost impossible to re-order all the balls by fifteen separate billiard players in one move reverse in the triangle”, says Peter.
“The second part of your example is good to follow, and almost everyone will find the example of spreading the billiard balls over the billiard sheet very recognizable. Almost everyone will see the spreading of the balls through the hit by the white ball as one outcome. But I expect that every single spread of the fifteen balls through the white ball is as unique - and has a chance more or less an equal order – as the fifteen players who have to play the 15 balls back into the triangle in one move each.
Or in a metaphor: every possible distribution of the 15 balls over the billiard sheet after a billiard push, is another book in the vast “Library of Possibilities". At the very back of the library there is a well-hidden cabinet with the "Books of Possibilities" to push the fifteen balls back in time within the triangle in the original order.
Because of the manner whereby we organize our observations, we will not regard this hidden cabinet of books in the “Library of Possibilities", about processes that went back in time as impossible options. The rest of the library is rather well known to us. These many books are about processes that in our eyes take place usually and regularly over time, although each known book is almost as unique as the limited number of unknown books in hidden cabinet of books in the back of the library.
I mentioned this metaphor of the "Library of Possibilities" because now I read a book about Sufism and Taoism, that describes that for Ibn 'Arabi – a Sofi philosopher – our tangible world of daily life is just a dream. We observe a lot of things with our senses, we distinguish them from one another, we put them in a sequential order, and ultimately we determine and conclude – on the basis of these observations – a certain reality around us. We call this reality and we do not doubt the authenticity hereof .
According to Ibn 'Arabi, this form of reality – based on sequential observations – is not a reality in the true sense of the word. This is not true "Being". For the reality that we experience, are only phenomena within the "Being", or in my own words: within the All-encompassing One. According to Ibn 'Arabi, the true "Being" is not perceivable to us, just as our everyday reality is also not observable to a person who is dreaming of daily life within her/his sleep ”, says Man.
“The physicist John Archibald Wheeler , who has introduced the name Black Hole, once summarised with the sentence "No phenomena is a real phenomena until it is observed"  the positivistic basis  for an important interpretation of quantum mechanics, wherein particles have no independent properties: when particles are not observed, these particles have no properties. I do not fully agree with this interpretation of quantum mechanics, that is also called the Copenhagen interpretation .
If I understand you well, Ibn 'Arabi combines the perceived tangible world – as phenomena in a dream – with the idealistic reality of the All-encompassing Being, that can usually not be perceived or perceived by humans. Do I understand you well?”, asks Carla to Man.
“I think you represent Ibn 'Arabi well, because although the reality of our daily life according to Ibn' Arabi is a dream, it is not a mere illusion, but it is a certain form of rendering – and self-manifestation – of the All-encompassing Being.
Everyday world of constant changes is an imagination and at the same time also (a part of) Being .
According to Ibn 'Arabi, the return to the All-encompassing Being requires a dying of this representation/image of the All-encompassing Being. An arising from the dream is necessary to awaken in Being in the true sense of the word. This dying is no physical dying in the common sense of the word, but leaving the dream of Being and of the phenomena within Being.
In my opinion, Ibn 'Arabi surpasses the Platonic allegory of the cave, where the chained prisoners observes reality as shadows on the wall of the cave .
In the view of Ibn 'Arabi, the phenomena – or the tangible world of daily life that people feel within like a dream of the All-encompassing Being – are part of the All-encompassing Being.
This reminds me of the haiku in “Emptiness” 
Way of emptiness
In everyday life,
Dream of all dreams.
Looking at our campfire, is this campfire dream or reality? I think dream and reality, and neither dream nor reality. The fire that we see, is a reflection of many complex burning processes  – come forth from the big bang – that altogether take care that wood with oxygen in a certain direction of time or "Arrow of time" according to Arthur Eddington, is converted into heat, light, ash and vapour of water. We experience these many burning processes as phenomenon "campfire", that is present as a veil in the change of the All-encompassing Being. The burning processes are reality, the phenomenon of "campfire" is reality and the change of the All-encompassing Being is reality. The campfire and the many complex burning processes are a dream of Being; the change of the All-encompassing Being is the "Dream of All Dreams". And thereby, these dreams are all empty within the "Being-whole" .
In the all-encompassing emptiness of "Being-whole", the many complex burning processes and the campfire progress not only in one direction, but also in the opposite direction: ashes, light and heat are converted within the "Being-whole" into wood and oxygen by photosynthesis .
I come back to my original question: why can’t we go back in time; why does our life go from the past to the future; why can’t we live from the future to the past? While in the emptiness of “Being-whole" life continuously comes forth from dying.
The processes of photosynthesis to wood for the campfire, and the burning of wood in the campfire to ash are cyclic and sequential in time. The process of this campfire will not reverse in time, so the flames will turn smaller and the ashes will turn into good wood for the campfire. This burning process of the campfire remains irreversible: it cannot be undone, so the time will develop from the present to the past. But in the "Being-whole" of the Earth, the processes of photosynthesis and burning progress simultaneously – of course in different places – side by side. Further on trees grow from wherefrom wood will be used for campfire by other people.
Carla, is it possible that time will stand still for us, and can we notice it? ” asks Man to Carla.
“Yesterday evening we have shown that an observer who passes the observation horizon of a black hole, will merge with the core of a black hole. Due to the enormous gravity, time will almost come to a standstill. But the observer will not be able to notice this stand still of time consciously.
I will try to find an answer to your question if we can observe a standstill of time in different ways. First, let’s look at our universe.
As far as I know, our universe is steadily expanding after the big bang. We note this through an even red shift  in the light of all galaxies around us. This means that everything around us all expands evenly. This means that "parallel" lines will also expand in the course of spacetime; hereby is the geometry of our universe is not Euclidean  but hyperbolic .
Just after the big bang, the four dimensions of spacetime are unfolded; and with this progressive expansion, all the four dimensions of spacetime around us are unfolding further and further. Hereby, spacetime has not yet come to stand still. It is not yet clear, whether our universe continues to expand, or that the universe will shrink again over time.
In my book on hyperbolic geometry is an image depicting our expanding in a schematic fashion: all polygons are equally large: the polygons at the edges are actually equal in size and expand as much as the polygons in the middle.
The woodcut Circle Limit III by Maurits Cornelis Escher gives a similar view. In an expanding universe, the squares on the edge are as large as the square in the middle, and all squares expand equally.
What is spacetime and how does spacetime expand?
In continuation of the special relativity theory by Albert Einstein from 1905, his professor mathematics Hermann Minkowski stated in 1908 at the 80th meeting of the Association of German Scientists and Physicians that:
"The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lays their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality." 
Before the concept of spacetime was accepted in science, scientists usually used "fixed references with points in space" (within a coordinate system), that did not change over time. In spacetime, this "fixed reference with associated points" can change over time according to a particular timeline.
In this schematic image – from the big bang to the present – the reference at the edge of the universe at "Inflation" follows the expanding timeline through "Dark Ages" and "Dark Energy Accelerated Expansion" to the reference in our time.
As a consequence, a reference circle at "Dark Ages" has expanded into a significantly larger reference circle in our time after around 12 billion years. And if we schematically render the volumes of the different periods after the big bang in a timeline, a four-dimensional impression in spacetime can be seen of the expansion of our universe after the big bang.
In this way, the 4 dimensions of spacetime are easy to make visible”, says Carla.
“In a similar way, a human life can be shown schematically in the four dimensions of spacetime. Instead of "Inflation" the young years, "Afterglow" becomes puberty, "Dark Ages” become adolescence, "Development Galaxies" becomes the years of wisdom, and the "Accelerated Expansion" is accelerated aging after the retirement”, says Man.
“With your background as architect, you have no trouble making this visible. Many people have trouble visualising the four dimensions of spacetime.
Not only the space of our universe changes over time, but also the time changes in the course of time. Both changes are well in line with our daily experiences, especially when speeds are well below the speed of light and acceleration within the human size.
But changes in spacetime differ considerably from our daily life, when travelling at speeds near the speed of light, when there are high accelerations or when the journey ends in a black hole. I will give a few examples hereof.
A photon  has no mass and it moves in free space at the speed of light . In a medium, a photon will be significantly decelerated: in special cases, a photon will move in a medium at a speed of less than 10 meters per second .
A photon is actually energy with an impulse; the energy of photons is determined by the frequency together with the amplitude of the vibration amplitude. The frequency is the number of vibrations per second, and the amplitude is the magnitude of the vibration.
Photons manifest themselves in experiments as particles and as waves depending on the way they are observed.
Over time, there has been a lot of discussion about whether photons should be seen as particles or as waves. Isaac Newton considered photons as particles because light – photons with a frequency of observable light – will give an impulse to an object against which light bumps. Christiaan Huijgens – and two centuries later Thomas Young and August Fresnel – considered photons as waves, because light has the characteristics of waves like refraction and interference.
This discussion was further complicated by the uncertainty principle  that was formulated by Werner Heisenberg in 1927. This uncertainty principle implies that there is a fundamental limit to the accuracy with which the location and impulse of a photon can be determined. This fundamental limit is primarily determined by the characteristics of the wave character of the photon. Freely rendered into our daily experience: the fundamental limit is determined by the peaks of the waves, that will always have a certain distance. The accuracy of the location of the wave will only depend on the distance between the peaks of the waves. Due to this wave character of the light, the maximum magnification of objects under a microscope will have a certain boundary that is determined by the frequency of light.
The same is applicable for the impulse : the summit of a wave causes the maximum pulse and the accuracy whereby the pulse can be observed depends on the distance between the peaks of the waves.
When the location and the impulse have to be determined more accurately, the frequency – and thus the energy – of the photon must increase. Among other things, due to this uncertainty principle – there are other reasons – fundamental accelerators need to be able to produce high energy. However, due to the golf character – with peaks and falls – the location and impulse cannot be determined accurately at the same time. When the location gets more accurate, the accuracy of the determination of the impulse decreases, and the other way around. The relationship between both is determined by Planck's constant  in the next formula where "?x" is the inaccuracy in the location, "?p" the imprecision imprecision and "h" Planck's constant.
I think this is still good to follow with common sense. Is this correct?”, says Carla.
“For me, it is easy to understand, but I also have a lot of background knowledge. Can you still follow it?”, asks Peter to Man.
“If I am not mistaken, the location and impulse of a photon are two different phenomena in a dream of reality. The impulse can hit us – just like an event in a dream – and the location is an illusion in the ever-changing and slipping away manifestation of the All-encompassing Being”, says Man.
“In my view, you are right, but some positivistic physicists will disagree fundamentally for a number of reasons. The results of quantum mechanical calculations do convince everyone, because of the high degree of repeatability and the very high degree of accuracy whereby the inaccuracy is determined. But the interpretation of the calculations has been discussed intensively without reaching an agreement.
At the edges of our perception, many mathematical problems – like dividing by zero and going to infinity – and interpretation problems come together. I will try to highlight a tip of this veil.
Let me start with a new “Gedankenexperimenten” or "Thought Experiments": let's travail on a photon – all of us naturally without mass – in free space towards a hydrogen atom, that is located at some distance with an electron at the lowest energy level. We take with us a reference clock, that is set at the same time as our time at home. Upon our departure, we enter the photon while it is moving slowly at a speed of 10 m/s through a transparent glassy material toward the free space. This slow speed of the photon is probably caused because the photon moves from atom to atom within the glassy material and taking some time rest at each atom.
The people at home are ready to say goodbye at the edge of the material when we depart into the free space. With a camera they make a video recording that can be shown at an extremely slow speed.
What will the people at home see at our departure?
First, they will see us clearly on a photon moving to the edge of the glassy material at a speed of 36 km/h. When we pass the edge of the material with the photon, we will immediately accelerate to the speed of light in the free space, and we immediately disappear; saying goodbye does not make sense. Fortunately, there is still the video recording. The people at home will show this video shot by shot at an extremely slow speed. On the recording they see us moving towards the edge of the material within the light of the photon, and then the image is black and remains black. Now they show our departure from the material at to the very slowest speed. They will first see the photon with us clearly within the material. With a very small chance and a some luck, the next image on the edge of the material is completely dark red, due to the decrease in frequency of the photon, because the energy of photon is moving to the free space (and by the diminishing energy, the frequency of the photon drops). The third image is black and a little vague: the energy of the photon has completely moved to free space, and upon leaving the material the photon has given a tiny impulse to the glassy material.
What do we experience, while traveling without mass with the photon?
First we move to the edge of the glassy material at a speed of 36 km/h. When we travel with the photon to the edge of the material, we might see through the glass – when the photon takes some rest at an atom – the people who stay at home passing by. At the edge of the material to the free space, we are accelerated momentarily from 36 km/h to the speed of light of 1.08 billion km/h in the free space. We do not notice anything of this acceleration, because we are without mass like the photon and therefore the force on our body is zero . We – traveling on the photon – do not observer anything, because no information from the past can reach us anymore. Also the reference clock has come to a standstill: the time axis within the photon has expanded to infinity .
Where are we after leaving the material with the photon?
That is unknown until the position of our photon is determined by an observation. It can be said with certainty that for the people at home – "observer" in the above schematic figure – we are somewhere inside the cone "future light cone" after leaving the material. In this figure, the time is displayed in seconds and the scale for "space" is light speed times seconds. The light speed in the "past light cone" had been 36 km/h, while the speed of light in the free space applies in the “future light cone”.
Because we – with the photon – have left the material in the direction of the time axis, we will have a high chance of staying near the time axis for the people at home – or “observer” in the above figure – at the time that corresponds to the time that has expired for the “observer” after our departure. But because of the uncertainty principle, we have a small chance of manifesting ourselves during an observation somewhere else within the future light cone. The chance that we will be observer near the edges of the future light cone is extremely small, but this chance is not zero. In quantum mechanics, the accuracy of this probability – in relation to other calculations and determinations in physics – is very high.
In the meanwhile, we travel timelessly until we clash with the hydrogen atom, that the photon – together with us – encounters like a flat disk/wave of energy. We are lucky, because the chance that the photon will come across a hydrogen atom is rather low: free space is very empty.
The energy and the pulse of the photon – so we also – cause that the electron of the hydrogen atom will move into a higher energy state: the ball/wave of the electron increases (according to the Compton Effect ) exactly in diameter, that the electron is in the next quantum state.
The energy and impulse of the photon that is not absorbed by the electron when the hydrogen atom increases to a higher quantum/energy state, continues its way into the free space. We stay behind within the globe of the hydrogen atom. Due to the small mass of the electron and the atom, our time axis has decreased from endless to a very high number, and the reference clock moves very slowly.
After a very long time – also due to slowly moving reference clock – we are accelerated again to the speed of light: the reference clock has come to a standstill again. We travel again with another the photon – with a slightly lower energy and impulse – with the speed of light through the free space.
For an outsider, the colour of the photon with us will exactly match one of the hydrogen atom's spectral lines : the atom has fallen back to the lowest energy level, and a massless photon has separated from the hydrogen atom at the speed of light.
Can you follow this thoughtful experiment? If so, I suggest to continue another time with the double split experiment , that shows the wave and particle properties of a photon”, says Carla to Peter and Man.
“The separate parts are not new for me, but you make a clear interconnection”, says Peter.
“I get the impression that the manifestation of events in the world of quantum mechanics depends on the observer. Is this right?”, asks Man to Carla.
“The events are universal, but the manner whereby the events are observed, depends on the observer's reference framework . The universal events manifest themselves differently according to the rules of general and special relativity theory to observers ”, says Carla.
“Can we observe events faster than the speed of light”, asks Man to Carla.
“No and yes. No, because photons are the fastest particles, that let us observe an event, or that can directly affect an event: this influence or change is "timelike" and sequential in time. And yes, when we look now from one side of the starry sky to the other side, we observe faster than the speed of light, but we cannot have an influence on the events on both sides of the starry sky: this observation is "spacelike", and the observed events take more or less simultaneously place without directly affecting each other”, says Carla.
“I see that the others are preparing for the night. I'm going to bed now too”, says Man.
“Yes, I am also tired; good night”, says Carla.
“Sleep well”, says Peter.
They are going to get ready for the night.
 See also: https://en.wikipedia.org/wiki/Entropy
 Source: White, Terence, Arthur, Koning voor eens en altijd, Utrecht: Het Spectrum, 1968, p. 38
 See also: https://en.wikipedia.org/wiki/Feynman_diagram
 Source image: https://de.wikipedia.org/wiki/Feynman-Diagramm. Remark: the time axis goes from bottom to top.
 See also: https://en.wikipedia.org/wiki/Photon
 Remark: In a Feynman diagram for the exchange of a photon between two positrons – or electrons with a positive charge – only the direction of the time axis has to be reversed from top to bottom.
 See also: https://en.wikipedia.org/wiki/Thought_experiment
 The human eye is able to observe a separate photon with the correct frequency within the visible light spectrum. Source: https://en.wikipedia.org/wiki/Human_eye
 The photons are displayed as yellow rays on the left side of this drawing. The "rods" and "cones" that can detect different types of photons, are shown on the right side of the drawing in the grey/brown area. In between there is (nerve) tissue that can absorb photons. Source image: https://en.wikipedia.org/wiki/Retina
 See also: https://en.wikipedia.org/wiki/Arthur_Eddington
 Source: Eddington, Arthur, Stanley, The Nature of the Physical World. New York: The Macmillan Company, 1929, p. 68 - 69
 The “arrow of time” goes in this drawing from A to B along the ruler. Source image: Eddington, Arthur, Stanley, Space Time and Gravitation. Cambridge: Cambridge University Press 1920
 Source image: https://en.wikipedia.org/wiki/Pool_(cue_sports)
 Source image: https://nl.wikipedia.org/wiki/Bibliotheca_Alexandrina
 Source: Izutsu, Toshihiko, Sufism & Taoism – A comparative study of key philosophical concepts. Berkeley: University of California Press, 1984, p. 7
 Source: Izutsu, Toshihiko, Sufism & Taoism – A comparative study of key philosophical concepts. Berkeley: University of California Press, 1984, p. 7
 See also: https://en.wikipedia.org/wiki/John_Archibald_Wheeler
 See: Kumar, Manjit, Quantum – Einstein, Bohr and the Great Debate about the Nature of Reality. London: Icon Books, 2014, p. 312
 See also: https://en.wikipedia.org/wiki/Positivism
 This is the so-called Copenhagen interpretation of quantum mechanics. See also: https://en.wikipedia.org/wiki/Copenhagen_interpretation
 Source: Izutsu, Toshihiko, Sufism & Taoism – A comparative study of key philosophical concepts. Berkeley: University of California Press, 1984, p. 8
 See also: https://en.wikipedia.org/wiki/Allegory_of_the_Cave
 Source image: http://nl.wikipedia.org/wiki/Allegorie_van_de_grot
 See also: Origo, Jan van, Who are you – A Survey into our Existence – Part 2: Five common realities – Emptiness. Amsterdam: Omnia – Amsterdam Publisher, 2015
 See also: https://en.wikipedia.org/wiki/Combustion
 See also: Origo, Jan van, Who are you – A Survey into our Existence – Part 2: Five common realities – Emptiness. Amsterdam: Omnia – Amsterdam Publisher, 2015, p. 55 et seq.
 Source image: https://en.wikipedia.org/wiki/Combustion
 See also: https://en.wikipedia.org/wiki/Photosynthesis
 Source image: https://en.wikipedia.org/wiki/Photosynthesis
 See also: Muller, Richard A. Now – The Physics of Time. New York: W.W. Norton & Company, 2016, p. 16
 See also: https://en.wikipedia.org/wiki/Redshift, and: Origo, Jan van, Who are you – A Survey into our Existence – Part 1. Amsterdam: Omnia – Amsterdam Publisher, 2012, p. 189 - 193
 See also: https://en.wikipedia.org/wiki/Euclidean_geometry
 See also: https://en.wikipedia.org/wiki/Hyperbolic_geometry
 Source image: https://en.wikipedia.org/wiki/Hyperbolic_geometry
 Source image: https://en.wikipedia.org/wiki/Circle_Limit_III
 See also: https://en.wikipedia.org/wiki/Hermann_Minkowski
 Source image: https://en.wikipedia.org/wiki/Metric_expansion_of_space
 Four-dimensional impression of the expansion in space of our universe after the big bang.
The image is made using a template available via: http://www.free-power-point-templates.com/
 See also: https://en.wikipedia.org/wiki/Photon
 See also: https://en.wikipedia.org/wiki/Speed_of_light
 See also: https://en.wikipedia.org/wiki/Slow_light
 Source image: https://en.wikipedia.org/wiki/Photon
 See also: https://en.wikipedia.org/wiki/Uncertainty_principle
 See also: https://en.wikipedia.org/wiki/Momentum
 Source image: https://en.wikipedia.org/wiki/Momentum
 See also: https://en.wikipedia.org/wiki/Planck_constant and Phillips, A.C., Introduction to Quantum Mechanics. Chichester: Wiley, 2009, p. 11 – 17.
 Source image: https://nl.wikipedia.org/wiki/Kwantummechanica
 The force on a body that is caused by an acceleration, is equal to the mass of the body multiplied with the acceleration. When the mass is zero, then the force on a body due to acceleration is also zero.
 The time dilation (expansion) “gamma” when traveling with the speed of light v = c can be determined by the formula:
When v = c, the denominator is zero and the time expansion “?” is infinite. This means that time has come to a rest on a photon; and as a consequence time stops to exist as any reference source. See also: https://en.wikipedia.org/wiki/Time_dilation
 Source image: https://en.wikipedia.org/wiki/Minkowski_space
 See also: https://nl.wikipedia.org/wiki/Compton-effect
 See also: https://en.wikipedia.org/wiki/Quantum_state
 The hydrogen atom is changed from quantum state 2.0.0 to quantum state 3.0.0 due to a partly merger with this photon. Source image: https://en.wikipedia.org/wiki/Quantum_state
 See also: https://en.wikipedia.org/wiki/Spectral_line
 Source image: https://en.wikipedia.org/wiki/Photon
 See also: https://en.wikipedia.org/wiki/Double-slit_experiment
 See also: Susskind, Leonard & Friedman, Art, Special Relativity and Classical Field Theory – The Theoretical Minimum. Toronto: Allen Lane, 2017, p. 48 - 53
 See also: https://en.wikipedia.org/wiki/Spacetime