“How “thick” are the “vibration planes” of electromagnetic waves (The electric field is in a vertical plane and the magnetic field in a horizontal plane).”
This question was posed recently on the forum of a LinkedIn group discussion of theoretical physics. On the face of it, it seems a serious question from someone who is seriously interested in in understanding the structure of EM fields. I take it up here because in its essence it exemplifies the problem I have with most of the current discussions in modern physics, the conflation between the description or conceptualization of an entity and the entity itself. If we take the question apart into its components, several things need to be asked at the outset. These include:
What does “thickness” mean in the study of a field?
Why is a wave typified as having a “plane”?
Assuming there are planes, in relation to what reference system can they be said to be “vertical” or “horizontal”?
How did it come to be that electric and magnetic waves are presumed to be at right angles to one another when combined in an EM field?
Wave phenomena are detectable in nature in multiple forms:
There are waves in strings, i.e. waves in one-dimensional objects. These are usually illustrated as sinusoidal forms in two dimensions, on paper or computer screen, although when viewed using slow-motion photography, they may also exhibit rotations, precession, or random disturbance in a third dimension.
There are waves we perceive in two dimensional objects, as in films or surfaces, that sometimes proceed in unidirectional form as in ocean waves before strong wind or current phenomena, radial procession, as out from point like disturbances, or multiple combinations of these, all typified by displacement from the presumed otherwise level surface of the originating medium.
And there are waves in three-dimensional media, as in sound waves in the atmosphere where the periodic variations detected are in the form of pressure or intensity differences in the medium, from strong to weak, from loud to soft, from high to low, etc.
What is common to all types of waves, of course, is that none of them consist of independent entities in and of themselves, but only as more or less coherent forms, disturbances, displacements in some medium, string like, plane like, or volume like.
Premise 1. A wave is nothing more than a perceived disturbance of its medium!
While it is true that from the first attempts, by Gauss, Faraday, Maxwell, to describe what an electromagnetic wave might be, the graphic techniques used were pen and paper, now computer graphics, but still planar. Occasional more three-dimensional techniques were employed as in isometric drawings. The result of this communication limitation was, as has also happened in the use of mathematics to describe physical phenomena, that the representation has taken the place of the phenomenon itself in the minds of the practitioners of physics.
Hence the question that prompted this discussion, and my response.
The NASA article referenced in the question makes an assertion unsupported by any information other the current assumption among scientists that empty space contains nothing. They make a distinction between the “mechanical” waves of water strings and air and “electromagnetic energy waves” that require no medium. Here is what they say:
“Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.“
How this occurs is left unexplained. The implication here is that “space” is truly a vacuum, not a medium. Hence, electromagnetic waves obviously don’t need a medium. But, of course, General Relativity strongly implies that “space” is a medium. It must be, since it is capable of being distorted. So two different realities are used to support two different assumptions. I am frequently reminded however, by experts, so to speak, that there are no contradictions in modern physics.
We are now, and were, in the time of the original wave theorists, able to detect the presence of magnetic or electric fields, which, though not discernible to our eyes or other human senses, we identified by the impact of their presence on other objects, events, or phenomena. In spite of our determination to define them as separate entities, in nature it is difficult to maintain that conceptual separation between electric and magnetic because they easily transform from one to another or into a combination that we call an EM field. Because of that combination, they are most commonly shown in the familiar form of a linear vertical-horizontal sine wave.
But remember, an electromagnetic field is a three-dimensional medium, despite its common depiction as a plane (with magnetic lines of force or currents). And waves in a three-dimensional medium must be more like the compression waves in the atmosphere that we call sound. So waves in an electromagnetic field must be disturbances in the pressure levels of that field, as in its inherent intensity, or charge. Let’s call these differences in energy density. Now this is hard to depict in a video or on a textbook page. This may be as close as we come in two dimensions.
If we are to explain how it is that light, microwaves, FM radio (even AM radio), the wireless access to what has become known as “the cloud”—all of these invisible wavelike phenomena we enjoy the fruits of are electromagnetic waves, then what could the medium be that they are “waves” of but an electromagnetic field itself?
Accepting this notion begins to explain things like the constancy of the velocity of light and other radiation currents, the capability of these to penetrate or be damped or absorbed by other entities, the presence of strong electromagnetic fields as concentrations of the general field and not as separate entities themselves.
Back to the original questions. What does “thickness” mean in a wave like this “compression-like” phenomenon we see in the second illustration? Where is the reference point or frame from which we can denote something as “horizontal” or “vertical? Do you see any right angles in the second illustration? And what part of this wave is the electrical part and which the magnetic? The assumptions underlying the original question are assumptions about a flawed graphic representation an electromagnetic wave, not about the “real” entity itself, so at its heart the question is meaningless.
And finally, why are our perceptions of reality so constrained by centuries-old graphic limitations that we cannot conceive of a three dimensional entity that we live in, are permeated by, and are an integral part of? Isn’t it time we shook off the conceptual constraints that have paralyzed our thought processes for the last two or three hundred years?