https://amsterdam.ninkilim.com/articles/light_energy_information_life/en.html
Few concepts have carried as much symbolic weight across human history as light. Long before we could measure its wavelength or calculate its energy, people sensed that light was more than a physical phenomenon - it was a metaphor for life itself.
In the Hebrew Bible, creation begins with the words: “Let there be light.” In the Qur’an, God is described as “the Light of the heavens and the earth.” In Buddhism, enlightenment is the state of awakening to truth. Across traditions, light is the manifestation of divinity, purity, and wisdom. Darkness, by contrast, is ignorance, evil, or chaos.
Our languages preserve these metaphors. We “shed light” on a problem, “see the light” when we understand, and call someone “brilliant” when they inspire. Knowledge is the light that banishes the shadows of ignorance.
Long before contemporary religions, cultures across the world marked the winter solstice - the shortest day, when darkness reaches its peak and light begins its return. For early societies, dependent on the sun for warmth and harvest, the solstice was a turning point of survival and hope. Fires, feasts, and rituals celebrated the rebirth of light. The tradition was later woven into Christianity as Christmas, yet the deeper symbolism remains: the renewal of life through the return of the sun. Even today, solstice celebrations remind us of light’s central place in human culture.
Light has therefore always been more than photons to us: it is energy, information, and life - in both the material and spiritual sense.
Having lived with its metaphors for millennia, humanity eventually turned to science to ask: what is light really made of?
A photon can be thought of as a microscopic antenna or a resonating circuit made of inductance and capacitance - except without any physical parts. It exists and propagates by continuously transforming electric energy into magnetic energy and back again, a self-sustaining oscillation that allows light to move through space.
Yet photons are not confined to the narrow band of colors visible to our eyes. They span an enormous range, from radio waves longer than skyscrapers to gamma rays smaller than an atomic nucleus. Across this spectrum, they shape the universe, sustain life, and power human civilization.
Every photon can be described in three interconnected ways:
These are tied together by the speed of light: c = λν. Longer wavelengths mean lower frequency and lower energy, while shorter wavelengths bring higher frequency and higher energy. The range is staggering:
This spectrum shows how the same quantum - the photon - expresses itself differently at different scales.
Different physical processes give rise to different regions of the spectrum:
In this way, photons arise from antennas, atoms, and nuclei alike, stitching together the physical universe.
Because photon energy is proportional to frequency (E = hν), radio-frequency photons have extremely little energy - trillions of times less than visible or gamma photons. As a result, antennas don’t emit one photon at a time in a way we can easily detect. Instead, they release vast numbers of photons simultaneously.
A single broadcast antenna may emit on the order of 10²⁰ to 10²⁵ radio photons every second. To any receiver - or to our intuition - this looks like a smooth, continuous wave. The quantization is still there, but it is hidden beneath sheer abundance.
By contrast, higher-energy photons such as ultraviolet, X-rays, and gamma rays carry enough energy individually to be detected one by one. Their particle-like nature is obvious, which is why Einstein’s explanation of the photoelectric effect focused on ultraviolet light, not radio.
This difference in perception is one reason the wave–particle debate persisted for so long.
Our understanding of photons has evolved over centuries of debate and discovery.
Feynman did not discover photons, but he gave us the most complete and accurate understanding of them, uniting centuries of conflicting theories into one coherent framework.
Beyond frequency, photons carry another property: polarization.
Because a photon’s electric field must always oscillate perpendicular to its direction of travel, it can orient in any angle within that transverse plane. Imagine a photon moving forward: its field may swing vertically, horizontally, or anywhere in between. This is polarization.
One of the most familiar consequences of polarization is glare. When light reflects off a flat, horizontal surface such as water, glass, or wet pavement, the reflected photons are not randomly oriented. The physics of reflection favors horizontally polarized light, because electrons in the surface re-radiate the electric field component that lies along the plane more efficiently.
This is why polarized sunglasses work so well: they contain a vertical polarizer, which blocks horizontally polarized photons while letting vertical ones pass. As a result, the glare from roads, lakes, and windshields is sharply reduced.
In the early days of automobiles, engineers even explored a grander idea: what if polarization could be built into the cars themselves? The proposal was to make all headlights vertically polarized, while fitting all windshields with horizontal polarizers. The result would be that oncoming headlights would be filtered out automatically, protecting drivers from glare. The concept was clever and elegant, but too costly for mass production at the time. The idea was abandoned - leaving sunglasses as the more practical solution to the same problem.
Polarization can also be more exotic. If the photon’s electric field has both vertical and horizontal components, and those components oscillate out of phase by a quarter cycle, the result is circular polarization. The field no longer swings back and forth along a single line, but instead traces a helix, spiraling around the axis of travel - a continuous sideways dance rather than a simple oscillation.
The analogy to a dipole antenna still holds: just as a dipole has blind spots along its axis, photons never point their electric field along their path. They remain transverse, always sweeping around their direction of motion.
On the quantum level, photons are emitted in sudden leaps.
Excited states may linger for nanoseconds or hours, depending on the system, but when emission occurs, it is instantaneous - a true quantum leap, with no halfway state and no partial photon.
This is the universal mechanism by which photons are born.
One of humanity’s greatest triumphs in harnessing photons is the laser.
A laser begins with a reservoir of atoms held in excited states. This population inversion is created by pumping energy into the medium - using an electric discharge, another laser, or a chemical reaction.
The excited atoms are trapped between two mirrors: one perfectly reflective, the other partially transparent. The spacing between the mirrors is tuned to match the photon wavelength. Only photons in resonance survive repeated reflections; the rest cancel out.
At first, emissions are random. Then one photon is emitted spontaneously along the axis of the cavity. That photon becomes the pilot, like the leader spark of a lightning strike. Its electric field defines the orientation and phase for all subsequent stimulated emissions. Neighboring atoms release photons that are exact copies - same frequency, same phase, same polarization.
As the pilot multiplies, photons bounce back and forth, reinforcing one another. When the intensity builds high enough, a stream escapes through the semi-transparent mirror.
The result is laser light:
Unlike the mixed, random light of a bulb, a laser is a disciplined army of photons marching in lockstep.
Photons are not just curiosities of physics - they are the foundation of the universe.
Every breath of oxygen, every meal, every phone call, every email depends on photons.
Photons are the quanta of the electromagnetic field, spanning a spectrum that powers stars, sustains life, and enables technology. They puzzled generations of scientists because they defied the categories of wave or particle.
The story of photons began with Newton’s particles and Huygens’ waves, grew with Maxwell’s equations, was sharpened by Einstein’s photoelectric effect, and finally found its clearest expression in Richard Feynman’s wristwatch analogy and the mathematics of QED.
From submarine signals to gamma-ray bursts, from antennas to atoms to nuclei, from sunglasses to lasers, photons are there. And through Feynman’s insight, we finally see them clearly - not just as waves or particles, but as the universal quanta of light.