Posts Tagged Gravitation

Why is the speed of light constant?

Why is the speed of light constant in the vacuum?

The constancy of the speed of light c in the vacuum was the key insight in Einstein’s work on relativity. However this was an assumption, rather than a proof.  It is an assumption that has worked well, in that the resulting theory has shown good agreement with many observations. The Michelson-Morley experiment directly tested the idea of Earth moving through a stationary ether, by looking for differences in the speed of light in different directions, and found no evidence to support such a theory. There is no empirical evidence that convincingly shows the speed of light to be variable in-vacuo in the vicinity of Earth. However it is possible that the speed of light is merely locally constant, and different elsewhere in the universe. In our latest  paper we show why this might be so.

Fundamental questions about light

There are several perplexing questions about light:

  • What is the underlying mechanism that makes the speed of light constant in the vacuum?
  • What properties of the universe cause the speed of light to have the value it has?
  • If the speed of light is not constant throughout the universe, what would be the mechanisms?
  • How does light move through the vacuum?
  • The vacuum has properties: electric and magnetic constants. Why, and what causes these?
  • How does light behave as both a wave and particle? (Wave-particle duality)
  • How does a photon physically  take two different paths? (Superposition in interferometers)
  • How does entanglement work at the level of the individual photon?

These are questions of fundamental physics, and of cosmology. Consequently there is on-going interest in the speed of light at the foundational level.  The difficulty is that neither general relativity nor quantum mechanics can explain why c should be constant, or why it should have the value it does. Neither for that matter does string/M theory. Gaining a better understanding of this has the potential to bridge the particle and cosmology scales of physics.

Is the speed of light really constant? Everywhere? At all times?

There has been ongoing interest in developing theories where c is not constant. These are called variable speed of light (VSL) theories [see paper for more details]. The primary purpose of these is to explore for new physics at deeper levels, with a particular interest in quantum-gravity.  For example, it may be that the invariance of c breaks down at very small scales, or for photons of different energy, though such searches have been unsuccessful to date.  Another approach is cosmological. If the speed of light was to be variable, it could solve certain problems. Specifically, the horizon, inflation and  flatness problems might be resolved if there were a faster c in the early universe, i.e. a time-varying speed of light.  There are several other possible applications for a variable speed of light theory in cosmology.

However there is one big problem:

In all existing VSL theories the difficulty is providing reasons for why c should vary with time or geometric scale.

The theories require the speed of light to be different at genesis, and then somehow change slowly or suddenly switch over at some time or event, for reasons unknown. None of the existing VSL theories describe why this should be, nor do they propose underlying mechanics. This is  problematic, and contributes to existing VSL theories not being widely accepted.

Cordus theory predicts the speed of light is variable, and attributes it to fabric density

In our paper [apr.v8n3p111] we apply the non-local hidden-variable (Cordus) theory to this problem. It turns out that it is a logical necessity of the theory that the speed of light be variable. The theory also predicts a specific underlying mechanism for this. Our findings are that the speed of light is inversely proportional to fabric density.  This is because the discrete fields of the photon interact dynamically with the fabric and therefore consume frequency cycles of the photon. The fabric arises from aggregation of discrete force emissions (fields) from massy particles, which in turn depends on the proximity and spatial distribution of matter.

This theory offers a conceptually simply way to reconcile the refraction of light in both gravitational situations and optical materials: the density of matter affects the fabric density, and hence affects the speed of light. So when light enters a denser medium, say a glass prism, then it encounters an abrupt increase in fabric density, which slows its speed. Likewise light that grazes past a star is subject to a small gradient in the fabric, hence resulting in gravitational bending of the light-path. Furthermore, the theory accommodates the constant speed of light of general relativity, as a special case of a locally constant fabric density. In other words, the fabric density is homogeneous in the vicinity of Earth, so the speed of light is also constant in this locality. However, in a different part of the universe where matter is more sparse, the speed of light is predicted to be faster. Similarly, at earlier time epochs when the universe was more dense, the speed of light would have been slower. This also means that the results disfavour the universal applicability of the cosmological principle of homogeneity and isotropy of the universe.

The originality in this paper is in proposing underlying mechanisms for the speed of light.  Uniquely, this theory identifies fabric density as the dependent variable. In contrast, other VSL models propose that c varies with time or some geometric-like scale, but struggle to provide plausible reasons for that dependency.


This theory predicts that the speed of light is inversely proportional to the fabric density, which in turn is related to the proximity of matter. The fabric fills even the vacuum of space, and the density of this fabric is what gives the electric and magnetic constants their values, and sets the speed of light. The speed of light is constant in the vicinity of Earth, because the local fabric density is relatively isotropic. This explanation also accommodates relativistic time dilation, gravitational time dilation, gravitational bending of light, and refraction of light.  So the speed of light is a variable that depends on fabric density, hence is an emergent property of the fabric.

The paper is available open access:


The fabric density concept is covered at

The corresponding theory of time, which predicts that time speeds up in situations of lower fabric density, is at



Citation for published paper:

Pons, D. J., Pons, A. D., & Pons, A. J. (2016). Speed of light as an emergent property of the fabric. Applied Physics Research, 8(3): 111-121.

Original work on physics archive (2013) :


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How does time-dilation work?

Schematic representation of asymmetric velocit...

Schematic representation of asymmetric velocity time dilation. The animation represents motion as mapped in a Minkowski space-time diagram, with two dimensions of space, (the horizontal plane) and position in time vertically. The circles represent clocks, counting lapse of proper time. The Minkowski coordinate system is co-moving with the non-accelerating clock. (Photo credit: Wikipedia)

We have an alternative way to explain this effect.

First, some background. Time-dilation is when clocks at different locations run at different speeds,  because of the different conditions at the two locations. Specifically, time passes slower in regions of  higher gravity (and faster in lower gravity). Likewise time runs slower for systems with higher acceleration, and faster in lower acceleration.

This has nothing to do with errors in the clocks. Nor does it matter what type of clock is used, mechanical or atomic. Instead time really does run differently, and it affects life itself. It is somewhat weird to think that your feet (which are in a slightly higher gravitational field) age slower than your head, but nonetheless your body still holds together! OK, the differences are not great, but it is the principle that counts. And the twin-paradox is downright spooky too.

The usual explanations for this involve the Lorentz equations, which allow the effect to be represented mathematically and quantified. But a deep explanation of what *is* time dilation is still lacking. It’s thought to be a property of spacetime, but that is only a partial explanation as spacetime itself is a mathematical model.

Moving beyond mathematical models and into ontological explanations is what the Cordus conjecture does well, and here again we have an alternative explanation. This offers an explanation of how time-dilation occurs at the subatomic level and then scales up to chemical bonds and ultimately to the mechanics of moving clock-hands and the physiology of living bodies.

For a start, we accept that time dilation does occur, and we accept also that atomic clocks do show a physical representation of that effect (as opposed to some other effect). Then we apply the Cordus model, whereby each particule has two ends which are energised in turn at its frequency. Now, (this next bit is important) energisation involves pushing discrete forces out into the external environment. So the frequency at which  this happens is affected by the conditions in the external environment. That external environment is the 3D world beyond the particule, and it does not matter if it is only a vacuum. (The Cordus fabric is the substitute concept for the spacetime of general relativity).

The external environment is what we call the fabric, and it comprises the discrete forces of all the other particules in the observable universe. All of which are likewise trying to push out discrete forces at their own individual frequencies. So what this Cordus theory offers is a way to understand the causality from the inner workings of the particle (the hidden-variables), to the discrete forces being produced at a frequency, to the cumulative effect (fields) of many particules affecting each other. The important insight provided by the Cordus theory is that the causality works in the reverse direction too. Thus the fabric, which is the cumulative effect of the discrete forces of many particules, has a way to cause the frequency of one particule to change. If we also adopt the Cordus idea that frequency *is* time for the particule concerned, then an explanation for time dilation is immediately  available.  Here it is:

The Cordus theory of time provides a mechanism whereby the external environment can push back in and affect the frequency of the particule. The proposed mechanism is as follows. An encounter with greater fabric density causes the frequency of a particule to slow down, hence time runs slower. This is because the high density of external discrete forces makes it difficult for the particule to emit its own discrete forces > emission is retarded >  energisation of reactive end is delayed > frequency lengthens.

It is known from general relativity that a body experiences time dilation in any of the following three situations: relativistic velocity, or acceleration, or in a high gravitation field. According to the Cordus time theory, all these are situations of  greater fabric density: the first because the fast-moving particule is at a speed approaching that of the fabric itself and therefore emission of the particule’s discrete forces is resisted (from the perspective of the particule, the external fabric is saturated),  the second because the accelerating particule emits discrete forces which it then moves into, thus creating its own locally high fabric density, and the third because high gravitation field is intrinsically a high external fabric density. In all these situations higher fabric density causes slowing of time. So Cordus also provides a single underlying mechanism for why these three situations are equivalent.

So to summarise, we have a mechanism to explain why the frequency of a particule is affected by velocity, acceleration, or gravitational field. How then does time dilation occur? Well, that’s also easy to explain, though it needs another piece of the Cordus theory. This is that the frequency of a particle determines the moments in time at which its discrete forces are available to interact with other particules. Particules only interact via their discrete forces. Those interactions are the basis for the strong force, chemical bonds, and the electro-magnetic-gravitational forces. (Cordus also provides a theory for the unification of the forces/interactions.) In turn these interactions determine the atomic structure, chemistry, kinetics and kinematics of the particule. And physiology is built on chemistry.

So anything, like fabric density,  that changes the frequency of a particule automatically changes the frequency of all of the mechanics, chemistry, and even life processes, with which that particule is engaged. This is what the fabric does, and it does it to whole assemblies of matter at once. Higher fabric density slows down the frequencies of all the particules in the object in that volume of space. And since, according to the Cordus theory, time  for a particule (or bonded assembly of particules) is nothing more than its frequency, when the frequency changes the passage of time also changes.

So that is why time-dilation is not simply a measurement effect, or a problem with mechanical time-pieces. Instead it slows down (or speeds up) the passage of time for all particules in that volume of space.

This understanding of time-dilation requires the Cordus theories for:

  • Frequency and internal structure of particules
  • discrete forces,
  • strong force
  • force unification,
  • time at the level of single particules
  • fabric concept

The existing theories of physics do not have this breadth of coverage, so if all of these really are necessary to explain time-dilation then one can see why Quantum Mechanics and General Relativity would struggle to explain it.

This Cordus explanation applies equally to a living body experiencing time-dilation. Thinking is a chemical process and Aging is a physiological process of chemical degradation, so any process that slows the frequency of the components of the atoms will also slow time. But this is no solution for longevity, because such a person would not experience any advantage, because their thoughts and movements would also be slowed. They would not be able to do anything more with their time. The only effect is that they would notice on meeting is that other people’s histories were compressed (or stretched).

Read more here:

Pons, D.J. (2013) What really is time? A multiple-level ontological theory for time as a property of matter. vixra, 1-40 DOI:

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