What Is Light?
A Detailed Explanation
Preliminary Remark
Light is one of the most important things in our world. It is through what we call light that we first acquired the ability to develop a visual perception of our reality at all. This sense has not always existed. To this day, more than 90% of all living organisms have no visual perception of their environment — at least not in the way humans do.
For a long time, we have perceived light as an independent thing — an independent entity. We believe we can generate light, or that light can be "swallowed." Based on observations, we have interpreted light as an electromagnetic wave that responds to magnetism, mass, and electricity, and that consists of photons possessing a very small mass.
And therein lies the core of the problem.
Seeing Is Not Understanding
Visual perception is not equivalent to reality. It is, first and foremost, a subjective reality. If several people see one and the same thing, this does not automatically mean they perceive the same thing — or interpret it identically.
Physics continues to puzzle over whether light consists of particles or is a wave. To resolve this definitional problem, one must first examine the interpretation more closely.
A wave, for example, is never an independent entity — it is only a mode of motion of an entity. Even if light were to move in a wave, it would not itself be a wave. The wave would be merely the manifestation of its motion. And for something to move in a wave, it requires a medium. Without a medium, without a carrier — no wave.
This gives rise to a simple question: if light is a wave — what is its medium? What does this wave move through?
And a further question anyone can ask themselves:
Who has actually ever really seen light?
The Invisibility of the Visible
Strictly speaking, everyone should answer this question with "No." For when a room is illuminated, we do see — but what exactly do we see? We see objects, that is, matter. And we may see the light source — a lamp, for example. But do we see something emerging from the lamp? No. We see absolutely nothing between the lamp and what it illuminates.
Light is invisible.
Outdoors, too, we cannot see light. We may see more, but the light itself remains hidden. This is astonishing when one considers that precisely what enables us to see is itself invisible to us.
What we can at most see are light sources — or the places where light strikes matter. But even then, we do not see light. For what we interpret as "light" in that moment is nothing other than a response of our optic nerves. They receive information — and above a certain quantity, they interpret it as "bright," "dazzling," or "uncomfortable."
When we look at the sun, it blinds us. It is painful; we instinctively avert our gaze. If we did not, our visual organs could be damaged. If we reduce the quantity of information — for example with sunglasses — we can observe the source. But do we then see the light? No. Even at the supposed source of light, we do not in reality see the light itself.
We have therefore interpreted and defined something that we cannot see at all.
A Fundamental Problem of Human Cognition
It is, of course, difficult to interpret something one cannot see. And this is a fundamental problem of human beings: we rely so heavily on our sense of sight that we equate it with reality. When it fails, our most important source of information is lost.
We already know this problem with air — a gaseous matter invisible to our eyes. And everything above it, in space, seems to hide even more from our senses: neutrinos, dark matter, dark energy, the presumed vacuum. There are evidently a number of things there that we — just like light itself — cannot see.
An Uncomfortable Thesis
What if I were to tell you that light — as we have understood it thus far — does not actually exist?
The majority would initially consider this mistaken. Here comes someone challenging something that has been interpreted and used for centuries, if not millennia. And yet one must — upon examining the facts above — ask: how do we know with certainty that something we cannot see actually exists as an independent entity?
It cannot be too small — we have microscopes. It cannot be too large — we have telescopes. We see photons, yes. But precisely here begins the problem that the famous double-slit experiment has been demonstrating to us for decades, without our having been able to resolve it.
The solution does not lie in quantum physics. It lies in the correct interpretation of energy.
The Actual Fundamental Problem
The fundamental problem in understanding light rests on a different, deeper fundamental problem: the missing understanding of energy.
Somehow we know that something is there. But to this day, we have struggled with its precise interpretation. Instead of a clear definition, we have created "forms of energy" — terms for energy when we perceived it in a particular action: kinetic energy, radiant energy, thermal energy, potential energy. Every time energy appeared in a new context, we gave it a new name, rather than recognizing that it was always the same energy.
And precisely this kind of fragmentation has prevented us from understanding light for what it is.
Light is energy.
But not quite in the way it is usually assumed. For even if light equals energy and energy equals light, one fact remains: we cannot see either of them.
What, then, do we actually see when we observe "light" — whether with measuring instruments or with our eyes?
We see an interaction.
The Ghost Under the Sheet
Energy and photons — these are the two main actors of this interaction. Both energy and photons are invisible to humans. Using certain methods, we can make photons visible — but only when energy is moving through them.
Only when energy is moving through the photons.
To better understand this process, we return to the definition of a wave.
Three Media, One Wave
A wave always requires a medium. Without a medium — no wave. We know waves very well, for example on water. Here, too, water is the medium and energy is the wave — because it is not the water itself that moves from A to B, but the energy within it.
Moving one level higher in matter density, we encounter the next perceptual problem: air. We can no longer see waves in air. We can feel them — as wind. We can hear them — as sound. The principle is exactly the same: a medium (gaseous matter) and a wave passing through it (energy). The only difference is that we can already see neither the energy nor the medium.
And now we come to light.
Here, too, there is a carrier — but this time, not matter in the classical sense as we know it from Earth, but photons. Photons are, in fact, also matter — like water, gases, or solids. But their density lies below what our senses can still perceive.
And precisely here lies the key:
Photons are only visible as long as energy is moving through them.
Before the energy wave — invisible. After the energy wave — invisible. As soon as photons no longer carry additional energy, they disappear for our eyes and our instruments.
And it was precisely in this way that the illusion arose that light is a wave of photons — just as one might think that an ocean wave is a wave of moving water. In reality, it is an energy wave moving through the medium.
The Core Statement
Light is the energy wave in the photon medium, as manifested to our senses.
It is not an independent phenomenon. It is not a particle. It is not a wave in the conventional sense. It is what happens when energy moves through photons — and we perceive the effect, not the cause.
The question "Is light a wave or a particle?" was never the right question. Photons are the particles — the medium. The wave is the energy moving through them. Both exist, but not as an either-or.
Water is the carrier; the motion is the energy. Photons are the carrier; light is the energy.
The double-slit experiment reveals no mysterious duality. It shows an energy wave moving through a medium, behaving exactly as waves do in every medium — it interferes, diffracts, superposes. That we simultaneously measure "particles" is because in that moment we are measuring the medium — not the wave.
Three Levels of the Same Principle
| Medium | Visible? | Wave | Perceived as |
|---|---|---|---|
| Water | Yes | Yes | Water wave |
| Air (gas) | No | No (only felt/heard) | Wind / Sound |
| Photons | No | No (only seen as effect) | Light |
The principle is identical at every level. Only the density of the medium changes — and with it, our ability to perceive it directly.
What This Means for Our World View
If light is not an independent entity but energy in a medium, an entire chain of puzzles resolves:
The artificial separation between "light physics," "wave physics," and "particle physics" becomes unnecessary. There is one principle: energy moves through media. Whether the medium is called water, air, or photons changes the scale — not the law.
It becomes explicable why we cannot see so much. Dark matter, dark energy, neutrinos — all of this is matter that does not back-couple energy to us. Just as air is "dark" to us because we cannot visually perceive its energy back-coupling.
And perception itself becomes newly interpretable. Our eyes do not see objects. They detect the energy back-coupling of matter. The "color" of an object is not a property of the object — it is the signature of the energy leaving it (Principal Theorem 4).
Light was never the mystery. The mystery was that we failed to recognize energy for what it is: the only wave that exists — in different media, at different scales, according to a single law.
The Law of Equalization.
Open Questions
- Precise measurement of photon density distribution in interstellar space
- Experimental verification that photons below the energy-wave threshold are truly invisible to all current instruments
- Mathematical description of the transition between sub-threshold and above-threshold photon states
Continue to Dark Matter or Principal Theorem 4 →