Reconsidering the Concept of a Medium in Modern Physics: The Electromagnetic Field's Role in Light Propagation

Author: Tom DeGerlia

DeGerlia Expert Consulting
Denver, Colorado 80205

For prepress review

Published: September 15, 2024

Introduction

The concept of a "medium" for light propagation was put to rest over a century ago since the famous Michelson-Morley experiment in 1887, which attempted to detect the presence of the "luminiferous ether" (Michelson & Morley, 1887). The failure of the experiment to confirm the ether's existence led to the wholesale rejection of the idea that light requires a medium to travel through space. While based on scientific evidence, this rejection has evolved into something more: a social and philosophical rejection of the very notion of a medium. Yet, in modern physics, as described under Quantum Field Theory (QFT), the role of the electromagnetic field in the transmission of electromagnetic energy closely mirrors that of a medium, even if we refer to it by a different word.

This demonstrates that subjecting scientific conclusions to popular opinion or any other social factor obstructs objective scientific discourse. While this technique can effectively control competing interests, it imparts a non-scientific bias into the scientific process that obstructs objective research and merit-based debate. My goal with this article is to shed light, via the history of the luminiferous ether debate, on how a clash between generations of physicists over the nature of light transmission resulted in a century of missed opportunities to better understand electromagnetic radiation.

Clash of the Physicists

In the late nineteenth century, classical scientists believed that light, as a wave, required a medium to propagate, much like sound propagates through air. This hypothetical substance, the "luminiferous ether," was thought to fill all space and provide the medium through which light propagates (Navarro, 2010).

Classical physicists felt strongly that light could be understood in classical terms and believed light to convey via a medium. Modern physicists, describing light behavior from quantum and relativistic standpoints, were at odds with classical physicists. This resulted in the marginalization of modern physicists initially, and after being ratified by a series of achievements, including the atomic bomb, the backlash against classical physicists was strong.

The Historical Rejection of the Ether

However, when the 1887 Michelson-Morley experiment failed to detect any evidence of this ether, it was concluded that no such medium existed (Michelson & Morley, 1887). The negative results of this experiment were seen as a victory for modern physicists and a defeat for classical physicists. They paved the way for Einstein’s theory of special relativity in 1905, which showed that light could propagate in a vacuum without needing an ether (Einstein, 1905).

Einstein's work revolutionized physics, but the resulting near-total rejection of the medium concept has distracted from the facts and threatens to perpetuate misinterpretations that don't consider what could be a more nuanced reality. According to the prevailing interpretation at the time, and as demonstrated by the Michelson-Morley experiment, electromagnetic radiation (like light) was defined as a form of energy that travels through the "vacuum of space" unobstructed, with space itself not offering any resistance or medium-like qualities. This interpretation led to the necessity for the photon, which was proposed by Einstein not as a definitive explanation but as one plausible hypothesis based on experimental outcomes (Einstein, 1905).

To exemplify this, here is an excerpt of a conversation with OpenAI ChatGPT-4 that expresses in no uncertain terms the current popular position of the scientific community:

User: "Is it possible that light is just energy propagating through some sort of medium that we cannot detect, like one of sub-atomic particles or otherwise?"
AI: "Light does not require a medium to propagate, as shown by the Michelson-Morley experiment, which disproved the existence of the luminiferous ether. Modern physics explains light as an electromagnetic wave consisting of photons, which can travel through a vacuum. While the possibility of an unknown medium or field isn’t entirely ruled out, no current evidence supports this idea."

The rejection was swift, blunt, and multi-faceted. The agent asserted with the same confidence and conviction it might have if asked:

User: "Is it okay if I forge a career taking candy from babies?"
AI: "No, it is not okay to forge a venture based on taking advantage of vulnerable individuals, such as babies, for profit. Such actions would be unethical and exploitative. Ethical business ventures should be based on fairness, integrity, and respect for others."

The latter seems to be a more commensurate response, given the wildly unethical assertion. This exemplifies that the popular view of physics concepts does not always align with modern physics. But more alarming, these same misconceptions are also commonly voiced by scientists.

The Electromagnetic Field: The Modern Interpretation

As our understanding of physics evolved, particularly with the introduction of Quantum Field Theory (QFT), the idea of fields became central to how we describe forces and particles. The electromagnetic field, for instance, is now understood as a pervasive entity that governs the behavior of charged particles and the propagation of electromagnetic radiation, including light (Feynman, 1985).

In classical physics, the electromagnetic field describes the region of space where electric and magnetic forces operate. With the development of QFT, the electromagnetic field is more fundamental; light itself is now understood as quantized excitations of this field, commonly referred to as photons. Light, therefore, does not simply travel through empty space but is a manifestation of the interactions within the electromagnetic field (Zee, 2010).

Social Rejection vs. Factual Rejection

The rejection of the ether wasn’t just a scientific rejection; it became part of modern physics's philosophical and social fabric. The word "medium" itself became associated with outdated ideas and the failure of classical physics to explain the nature of light. The scientific community was eager to embrace the new, more elegant solutions of relativity and quantum mechanics, and with them came the rejection of anything resembling the ether (Navarro, 2010).

But this rejection was never a factual one in the broader sense. While the luminiferous ether, as initially conceived, did not exist, under QFT the electromagnetic field serves a very similar purpose in modern physics. It fills space, interacts with matter, and governs the propagation of electromagnetic waves. To deny that this field behaves in some ways like a medium is to ignore the underlying physical reality (Feynman, 1985; Zee, 2010).

The Marginalization of Classical Physicists

After the Michelson-Morley experiment in 1887 and the rise of Einstein's theory of relativity in the early 20th century, many physicists who had built their careers around the luminiferous ether faced professional marginalization. As Jaume Navarro argues in his paper, the decline of the ether was not solely based on experimental outcomes but was shaped by historical and philosophical shifts that reframed the ether as an outdated concept (Navarro, 2010). Prominent physicists, eager to embrace Einstein’s elegant solutions, contributed to the ether’s downfall by framing it as irrelevant to modern physics.

Despite this, the ether theory wasn’t immediately abandoned. Historians and physicists were eager to distance themselves from the ancients, concluding that the ether was no longer relevant, leading to its eventual disappearance from the scientific lexicon. Those who continued to advocate for the existence of the ether faced intellectual isolation and were professionally sidelined as modern physics embraced the photon model (Navarro, 2010). This form of intellectual exclusion stifled discourse about media-based light properties, creating a barrier to exploring these concepts openly.

Furthermore, Einstein himself acknowledged that while the luminiferous ether was unnecessary for his theory of special relativity, the concept of an ether-like medium was not entirely discarded. In his later work on general relativity, Einstein stated that space itself, with its physical properties, could be viewed as a form of ether—just not the mechanical ether of classical physics. This shift highlights that even Einstein saw the necessity of a medium-like behavior in the conveyance of electromagnetic energy, a view that mirrors the intentions of the original ether theory (Navarro, 2010).

Revisiting the Medium Concept

It's time to reconsider the term "medium" in light of what we now know about fields and forces in physics. The electromagnetic field acts as the substrate through which electromagnetic waves propagate, and in that sense, it fulfills the role of a medium (Feynman, 1985; Zee, 2010).

We don't need to return to the outdated and debunked notion of a luminiferous ether, but we should recognize that our rejection of the word "medium" is based more on the ether's historical baggage than on the realities of how light and fields interact. The electromagnetic field, as described by QFT, is a modern and more accurate representation of what physicists once sought to describe with the ether, but we can’t allow semantics to get in the way of understanding its true nature.

Treating Theory as Law is Problematic

However, when a conclusion is elevated in credibility beyond its merits, we risk closing our minds to possibilities that still exist. The behavior of light is well understood in many contexts, but when ideas like "photons" are treated as absolute law, it leaves little room for reinterpretation or the exploration of alternative explanations. While photons are essential for explaining quantum phenomena, this does not mean they are the only way to describe light in all contexts.

By treating certain models as definitive, we risk hindering the development of new theories or explanations for existing phenomena.

Science, at its core, should remain open to re-evaluation and reconsideration, especially when the conclusions drawn are based on historical rejection rather than present evidence. The idea that the electromagnetic field could act as a medium for light propagation is one such area deserving further consideration.

It's Okay to Separate Facts from Opinions

Rely on the facts and treat the explanation as conjecture until proven otherwise. At any given time, the accuracy of our conclusions is often far lower than the accuracy of the observations that fueled them. It's okay to say, "light factually behaves in this way, and one model that describes this accurately is the photon model." It would be far less accurate to say, "light behaves in this way because of how the photon factually behaves." The conclusion is often far more hypothetical than the observation.

A Factual Premise Supports a Logical Conclusion

A common response I receive when speculating about the nature of light is, "photons require no medium to travel through the vacuum of space." When stated with authority, this assertion sounds like a ratified conclusion, initially serving to discourage free thought. Effectively saying, "that's silly to even consider, everyone knows how light works." However, a closer inspection reveals that it lacks a solid factual foundation. A photon is an explanation for the observed behavior of light, given certain constraints, one being that "photons don't require a medium."

Given that the Michelson-Morley experiment did not account for all possibilities, the experimental setup could not possibly rule out a "medium" that could convey light energy but rather ruled out the luminiferous ether as it was hypothesized at the time. Additionally, modern physics, under QFT, recognizes the electromagnetic field as the field through which electromagnetic energy, including light, travels. Therefore, the conclusion that "photons need no medium to travel through the vacuum of space" relies on the premise that there is no medium and that there is a vacuum, neither of which is accurate under modern physics. This exemplifies the logical fallacy of using the conclusion to justify the premise.

Break Free from Semantic Bias

The scientific community's aversion to the word "medium" is rooted more in history than in science. The electromagnetic field acts in ways similar to what classical physicists imagined for the ether—it is a pervasive field that allows the propagation of electromagnetic energy. Acknowledging this does not mean returning to pre-relativity physics but rather embracing a more nuanced understanding of the role that fields play in the universe.

For over a century, since the luminiferous ether was invalidated, in our rush to discredit the old and usher in the new, we made the presumption that there is a vacuum of space and that electromagnetic energy must be conveyed via particles, thus leading to the photon theory.

While this picture may prove accurate, there is no reason in science to extend that status in advance of this proof.

Ultimately, this is not about resurrecting outdated ideas, but about letting go of a bias that has no basis in modern physical theory. The electromagnetic field is, in effect, a medium, and recognizing this can only enhance our understanding of the fundamental nature of light and energy.

References

Einstein, A. (1905). Concerning an heuristic point of view toward the production and transformation of light. Annalen der Physik, 17, 132–148.
Feynman, R. P. (1985). QED: The strange theory of light and matter. Princeton University Press.
Michelson, A. A., & Morley, E. W. (1887). On the relative motion of the earth and the luminiferous ether. *American Journal of Science*, 34(203), 333–345.
Navarro, J. (2010). Killed by its own obituaries: Explaining the demise of the ether. Science in Context, 23(2), 175–203.
Zee, A. (2010). *Quantum field theory in a nutshell*. Princeton University Press.

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Reconsidering the Concept of a Medium in Modern Physics: The Electromagnetic Field's Role in Light Propagation