Physicists Calculate That 'Cutting' a Photon Could Generate Infinite New Particles

In the classical understanding of physics, elementary particles are the absolute bedrock of reality. By definition, a fundamental particle like a photon—the basic unit of light and electromagnetic force—cannot be divided into smaller components. It is the smallest possible packet of energy, possessing no mass and traveling at the absolute speed limit of the universe.

But the quantum realm operates under a notoriously bizarre set of rules, prompting a team of theoretical physicists from the University of Oslo to ask a seemingly impossible question: what would actually happen if you tried to cut a single photon in half anyway?[2]

Their findings, recently published in the journal Physical Review Letters, reveal a mathematical paradox that defies common sense. Slicing a photon wouldn't yield two half-photons, nor would it simply destroy the particle. Instead, the act of cutting it would violently disturb the quantum vacuum, potentially spawning an infinite swarm of brand-new light particles out of thin air.[2]

To understand this phenomenon, one must look at the wave-particle duality of light, a concept first demonstrated by British physicist Thomas Young in 1801. While a photon is a discrete, indivisible particle, it simultaneously exists as an extended wave of probabilities stretching through space.[1]

Johannes Skaar, a theoretical physicist at the University of Oslo, and his colleagues designed a rigorous mathematical thought experiment to intercept this wave. They imagined a single photon traveling toward a highly specialized optical shutter—essentially a perfectly reflective mirror capable of moving at impossible speeds.

In their theoretical model, the front half of the photon's extended wave hits the mirror and bounces back in the direction it came from. But precisely at the halfway point of the wave's length, the mirror is instantly removed, allowing the back half of the wave to pass straight through unimpeded.

This sudden truncation acts like a guillotine on the photon's waveform. Because the universe abhors a sudden, sharp edge in a quantum field, this abrupt, discontinuous change tugs violently on the underlying fabric of empty space.[1]

In quantum physics, empty space is never truly empty; it is a bubbling vacuum of potential energy and virtual particles popping in and out of existence. The extreme energy required to remove the mirror instantly rips real, permanent photons directly out of this vacuum state.

The resulting mathematical state is a complex quantum superposition. If you were to measure the outcome of this severed wave, you wouldn't find a neatly divided particle. Instead, you would find a probability of generating anywhere from zero to an infinite number of new photons.

The speed of the cut dictates the scale of the resulting swarm. If the mirror is pulled away relatively slowly, the disturbance to the quantum field is minor, and the math suggests only a few extra photons might emerge from the vacuum.

However, as the speed of the mirror's removal approaches infinity, the mathematical limit of the resulting superposition also approaches infinity. An infinitely fast cut produces an infinite number of particles, transforming a single photon into a blinding burst of light.

Independent physicists initially viewed the dramatic claim with skepticism. Daniele Faccio, a physicist at the University of Glasgow who was not involved in the research, admitted his first reaction to the premise was that it was "nonsense."

Yet, after reviewing the rigorous quantum field theory equations laid out by the Oslo team, Faccio and others conceded that the math is entirely sound. The technique is legitimate, and the results, while mind-bending, are an accurate reflection of how quantum fields behave under extreme stress.

Skaar himself is quick to emphasize the practical limits of the thought experiment. An infinitely fast mirror removal would require infinite energy, which violates the fundamental laws of physics. Therefore, a true infinite swarm can never be generated in a real laboratory.

Even so, the thought experiment exposes a profound truth about the nature of reality. It demonstrates that the properties of a single particle are inextricably linked to the vacuum of space around it, and that observing or altering one inevitably disturbs the other.

Ultimately, the "truncated photon" serves as a powerful reminder that at the most fundamental levels of existence, the universe is far more interconnected—and far stranger—than our macroscopic intuition can ever fully grasp.[1]