Aug 14, 2017 - Mechanics and Relativity are considered in the argumentation, but also ... introduce an invisible actor (first cause or God) in his philosophical ... concepts in modern physics are closely related to metaphysics. ... changes position with time, and the most rapid particle, the photon .... Other speakers were:.
The strange properties of photons
Abstract When dealing with extremely small and rapidly moving particles, the two great theories of modern physics, Quantum Mechanics and Relativity have to be taken into account. This is especially true for the photon with mass zero and travelling at the speed of light, the maximum speed allowed in Relativity. Strange result are expected, see for example the delayed choice Gedanken-experiment of Wheeler about light travelling over astronomical distances. There is evidence that causality in this and other situations has its origin outside the realm of time. For the philosopher it is a challenging task to understand the observations of the physicist and apply the metaphysical concepts time, space, causality, choice and others adequately. In this talk an attempt is made to look at the challenging behavior of the photon as a physicist as well as a philosopher. For more related work, see slide 34.
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The strange properties of photons
In a previous article Driessen et al. *) showed evidence that a photon on its trajectory from emission to absorption undergoes causal influences from the final state separated in time and space from the initial state: nonlocality and nontemporality. The argumentation was mainly based on quantum mechanics and more precisely the Heisenberg uncertainty principle. In this study a broader view is taken: not only physical theories like Quantum Mechanics and Relativity are considered in the argumentation, but also philosophical issues. Philosophy is highly relevant as causality and time and space are basically philosophical concepts. In the discussion philosophical systems are mentioned which relate present events to causes from outside time, or otherwise deny this possibility. *) Evidence for nonlocality and nontemporality of a single photon, A. Driessen, 2003 (unpublished), 2017 https://arxiv.org/abs/1707.08034
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The strange properties of photons
In the introduction we focus first on Plato and the cave allegory (Plato, Republic 514a-520a). The main conclusion is that, according to Plato, a invisible, eternal reality is at the origin of the visible world.
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The strange properties of photons
It is worthwhile to view this 3-minutes video. It ends with the phrase: They (the men inside the cave) cannot understand his (their friend who has been outside the cave) fantastic stories of the world outside of the cave. To them it will never exist. This of course does not make the world outside of the cave any less real.
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The strange properties of photons
In this slide a summary is given of the cave allegory and more general the classical philosophy including Aristotle. The main point is that reality is not restricted to the visible or otherwise observable world, but includes also invisible not observable beings. In Plato, the eternal ideas, and in Aristotle, e.g. the first cause. But even more challenging is the statement of both philosophers that the invisible is cause of the visible.
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The strange properties of photons
Another philosopher, Laplace, excludes explicitly the logical necessity to introduce an invisible actor (first cause or God) in his philosophical system.
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The strange properties of photons
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It may seem strange that in the following philosophical and physical arguments are mixed together. But as De Broglie points out certain central concepts in modern physics are closely related to metaphysics. On the other hand can be said that in a certain way also metaphysical concepts gain in richness when confronted with the results of modern science.
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The strange properties of photons
Here a schematic overview of different views are presented according to the cave paradigm. Inside the cave: the visible and observable world; outside the cave: the invisible world, acting on the events inside the cave.
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The strange properties of photons
This section and the following one is focusing on physics. The first one on the theory of Relativity of Einstein, the second more on the properties of a photon. The slides of Relativity had been used by the author as an introduction in the context of a course on Electromagnetism at the University of Twente.
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The strange properties of photons
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This is a space-time diagram with 2 spatial and 1 temporal coordinate. In reality, of course, one has to deal with three spatial coordinates, but the imaginative power of humans prohibits to sketch a pseudo 4dimensional cone.
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The strange properties of photons
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Roger Penrose is a master in visualizing the geometry of Relativity, see *). In the following several time figures from his work are used. Here schematically the step from special to general Relativity is explained by introducing curved space: the light cones now are allowed to incline with respect to each others. With other words time flows different in different places. *) R. Penrose, Cycles of Time, Random House, London 2010
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The strange properties of photons
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To simplify we restrict now to only one spatial coordinated. Three examples of constant moving objects are given in the left figure: a particle at rest is moving in time without changing its spatial position. A rocket changes position with time, and the most rapid particle, the photon follows a largely inclined line that defines the light cone. The right figure states that physical causes have to restrict the speed of propagation to a maximum: the speed of light. As consequence only events within the past light cone may have causal influences on a event located in the origin. Alternatively only events within the future light cone may undergo causality from an event on the origin.
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The strange properties of photons
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We start now a series of Gedanken experiments with moving trains. First we consider a train at rest. By advancing in time, no position is changed.
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The strange properties of photons
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Now the train is moving to the right.
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The strange properties of photons
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In addition to the previous slide we introduce in red the coordinates of the moving train. By allowing tilting of the time coordinate we clearly enter the field of general Relativity.
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The strange properties of photons
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Now we consider two events, one at the origin and one outside the light cone. The statement now is that there is a inertial system where these events are simultaneous. To “prove” this we consider a train moving to the left. Both events now have the same time-coordinate. They are purely space-like separated.
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The strange properties of photons
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Now we consider two events where the first is at the origin, the second within the cone. The statement now is that there is a inertial system where these events are at the same place. To “prove” this we consider a train moving to the left. Both events now have the same spatialcoordinate. They are purely time-like separated.
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The strange properties of photons
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Now we consider two events where the first is at the origin, the second on the light cone. The statement now is that there is a inertial system where these events are simultaneously and at the same place. To “prove” this we consider a train moving to the left with the speed of light. Both events now have the same spatial-coordinate. But there is also time dilatation: the time interval becomes zero.
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The strange properties of photons
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The consequences for a photon are remarkable: In the coordinate system of the photon, the event of emission and absorption is instantaneously and without distance. In the next section these strange properties of a photon are discussed in more detail.
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The strange properties of photons
In this section the findings of three scientists: Roger Penrose, John A. Wheeler and Adriaan Fokker are presented.
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The strange properties of photons
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This figure is taken from Penrose and illustrates the formation of a black hole. Time is passing from below upwards. In the beginning matter is collapsing to the center. To illustrate the curved space, light cones at different positions from the center of the black hole are drawn. Approaching the black hole the light cones are increasingly inclined. Once at the horizon the point of no return for a photon- the time line for a photon, i.e. the cone, is oriented parallel with the horizon. The cone itself becomes more and more compressed because of time dilatation.
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The strange properties of photons
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This figure is an enlarged detail of the previous one. Relativity states that the speed of light is a constant in all coordinate systems. If one approaches the black hole, the cone becomes more and more inclined such that at the horizon the change in the x direction, Δx is approaching zero even for a photon. This implies that with constant c also the change in time Δt is diminishing accordingly. Time is not passing any more: complete time dilatation.
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The strange properties of photons
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One could dream of a local clock at the position of the light cones that could be read from distance. And, happily enough, this clock exists. An exited atom emits radiation with a frequency of ν defined by ΔE=hν, where ΔE is the energy difference between the excited and the groundstate of the atom and h the Planck constant. This means that atoms in an inclined light cone will emitt radiation with a certain red-shift. In the case of optical radiation, ν is in the order of hundreds of THz. The experimental observation of the optical spectrum of astronomic objects is a well developed technology. This gravitational red-shift has been experimentally observed, in addition to the cosmological red shift related to rapidly moving objects.
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The strange properties of photons
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Roger Penrose is quite clear in his statements regarding photons and time. Above a copy of a slide in a public lecture in Leiden on 10-6-2011 is given: Eternity is no time at all, for a photon. In his book, Cycles of Time, Random House, London 2010, p. 146, he states: The point is that, according to a massless particle, the passage of time is as nothing.
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The strange properties of photons
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In 1978 John Archibald Wheeler made a far-reaching proposal for a cosmic delayed-choice interferometric set-up. The interferometer consists of a quasar, a gravitational lens in front of it and a detection set-up on earth positioned billions of light-years away. The detection set-up is alternatively a telescope or a interferometric set-up. In the latter case interference is observed indicating that the photon follows both paths around the gravitational lens. If alternatively the telescope is chosen, all photons are uniquely related to a specific path. The present choice on earth determines the path of the photon followed billions of years ago.
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The strange properties of photons
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In 2013 Van der Wel et al. observed an astronomic constellation which resembles the geometry of the Wheeler proposal. It consists of a source galaxy nearly 11.5 billion light years away behind a gravitational lens at a distance of about 9,5 billion light-years from earth. Clearly 4 images of the source can be observed. By the way, this picture is in good agreement with the distribution of light cones in the neighborhood of a heavy object as schematically plotted in slide 21 (taken from Penrose).
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The strange properties of photons
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Adriaan Fokker is a Dutch scientist, who worked a period together with Einstein and wrote the first Dutch textbook on relativity; in 1965 appeared the English translation at Pergamon Press in Oxford: Time and Space, Weight and Inertia. This book inspired the approach in slides 12 to 19. He confirms the occurrence of zero intervals, connecting events which are located by observers with spatial distance and temporal duration between them. In the introduction he develops some speculative ideas and relates explicitly his findings in physics to a reality outside the realm of physics. He states: The mathematical formula is quite simple and plain, nevertheless it relates to one of God's secrets and implies His sempiternal ubiquitous presence.
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The strange properties of photons
A seemingly bizarre road has been followed: starting with Plato’s cave allegory we ended up with really weird conclusions about photons. But from the point of physics, relativity is a well established theory again and again confirmed by experiment. But now we take the highly speculative conclusions from physics and enter again philosophy.
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The strange properties of photons
This slide has been shown in the introduction (slide 8). Now we extend the table with additional rows.
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The strange properties of photons
If we consider the results from physics we could say that we are inside the cave. But it appears that outside the cave, we find more than an unnecessary hypothesis. For Plato, outside the case we find the world of the eternal ideas. In the case of relativity, we find objects outside time: the photon. Penrose states, eternity is no time at all for a photon. Wheeler considers delayed choices, i.e. causality from outside time. And Fokker demonstrates evidence for ubiquitous presence outside time.
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The strange properties of photons
The slide before we mentioned causality from outside time in connection with Wheeler’s proposal. Perhaps it is worthwhile to focus a little bit on the metaphysical concept “causality”. In classical philosophy, the principle of causality states: whatever is moved is moved by another or whatever is changed is changed by another. The first cause or the unmoved mover does not enter this proposition, it moves or changes others, but it is not moved or changed by anyone or anything. A representative of English empiricism, David Hume, denies the principle of causality by restricting human knowledge to the pure observation of objects one following the other. Whether it is caused is beyond human knowledge. Stephan Hawking is using in some way the classical principle of causality, but with an important restriction: only causes in the past may produce effects in the present. For a discussion, see A. Driessen, The question of the existence of God in the book of Stephen Hawking “A Brief History of Time”, Acta Philosophica, 4 (1995) 83-93. The question now remains, which philosophical concept of causality is able to deal with delayed choice experiments or causality from outside time.
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The strange properties of photons
If one reads works of classical philosophy, e.g. Aristotle, one encounters a special approach: the philosophical statements are illustrated and developed by human experience which includes all scientific results available to a certain philosopher. In ancient Greek is was possible that a single human has a complete view on the scientific knowledge of his time. This has changed dramatically. The current knowledge in science has increased so much that only a strong specialism is able to access the stateof-the-art of science in a certain field. But how can it made possible that the philosophical relevant findings of science can be made known to philosophers. On the other hand, scientist are confronted with philosophical issues in their science and are not able on their own to treat them adequately. It is a dream of the author that the dialogue is intensified between scientists and philosophers to end up with a consistent view on reality. It’s a realistic dream, however, as the results of science support an optimistic view on the human intellectual capacity.
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The strange properties of photons
This talk had been given at one-day symposium on: Science, Reason and Faith: Causality, Time and Origin of the Universe. Other speakers were: Christian Marinoni : Chaos et causalité dans l’univers : cinq questions simples pour une perspective d’ensemble. Carlo Rovelli : Dans la chaine de causalités y a-t-il de la place pour des choix libres ? Antoine Suarez : Non-localité, temps et relativité. Jean Paul Kneib : Les grandes énigmes de la cosmologie moderne et nos projets pour les résoudre. Étienne Klein : Que reste-t-il de l’idée de cause en physique ? Cyrille Michon : Mots de fin du colloque.
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The strange properties of photons
A page added in 2017 to present an overview of related work by the author.
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