Posts Tagged Relativity

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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Reality and apparent simultaneity

One of the long-standing philosophical questions is whether there is a reality to what humans experience. One of the famously controversial ways to looking at this is the holographic principle, which proposes that everything we experience in 3D is merely a holographic projection of 2D information on the outside surface of the universe.

That raises a second question, which is how my experience of reality is connected and coordinated with yours. This introduces time into the problem. Special relativity (SR) has a principle, in the form of the relativity of simultaneity, that says that the order in time of two spatially separate events cannot be determined  absolutely, but instead depends on the motion of the observer. Thus it is impossible to order two events in time if they occur in different places (hence difference frames of reference).

In our Cordus theory of time, we examine some of these questions. We look at the question of how multiple bodies interact, and how the coordination arises. We have already identified that there is no master clock, but if that is lacking then we still need a coordination mechanism. There is a connectedness of phenomena that are at different geometric locations. It seems that spacetime is continuous, because it seems that it is possible to coordinate the two phenomena in time. We show that the two phenomena are linked, because they share the same fabric.

According to this new perspective, any communication between two objects is a result of photons, or massy particules, or fields, and these cause positional constraints on the other, i.e. the geometric location of the reactive end is affected by the communication. A phenomenon that occurs in one volume of matter, be that combustion, noise, motion, etc,  thereby communicates that to other matter around it. Consider one volume to be my body: my speaking transmits forces to the volume of air immediately around me, which in turn propagates the dynamic displacement throughout its bulk, so that the membrane in your ear is displaced, and you hear the sound.

In general the phenomenon is that one volume of matter causes an effect in the second. The interactions at the most basic level all require frequency cycles, so this causes temporal causality.  Thus we infer:

It is not a master clock that accomplishes the temporal connectedness of phenomena that are at different geometric locations, nor does it require continuity of spacetime per se. The piece-wise communication, via discrete field interactions of the fabric, between adjacent volumes of space (matter and fabric) applies spatial consistency to time.

Any one particule A receives discrete forces (fields) from all the particules (many Bs) in the observable universe. Space within the universe is therefore filled with a mesh of  discrete fields in transit, which in the Cordus theory is termed the fabric.

Fabric time is the mutual interconnectedness of matter particules spread over three-dimensional space. This occurs via the fabric, comprising discrete field forces for electric-magnetic-gravitational interaction. Not strictly a time, this is rather  a coordination of events across space.

In this theory the fabric, and the EMG fields it carries, causes a connectedness between particules. They respond together, even if in a slightly delayed manner as their separation increases. There is therefore a coherence and smoothness to the interaction between particules, mediated by the fabric. The resulting interaction stitches together three-dimensional domains of space (matter and vacuum-fabric) into a macroscopic collated time. This level of time passes more slowly, due to the many tiny delays required for particules to react to each other, given the dissimilar-frequency and phase-differences between the particules.  This, Cordus suggests, is where the arrow-of-time arises,  and what general relativity perceives as spacetime. This is also the macroscopic level of physical time, and hence where our perception of time first arises.

This Cordus concept of 3D fabric affirms the general relativity perspective of spacetime.  It also provides an ontological answer to one of the earlier questions: it suggests that spacetime has a quasi-substantial status (comprises discrete force) but has no universal time-signature per se, and mainly represents merely the relationships between bodies.

Read more about the Cordus time theory 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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