A photon is a fundamental particle of light that cannot be divided under normal conditions. Interestingly, photons do not possess a definitive position; they exist as an extension of an object rather than as a distinct particle.
So, what occurs if a photon is midway through reflecting off a perfect mirror when we pull the mirror apart? The intriguing answer comes from a team of Norwegian physicists: It has proven (arxiv.org link) to be far more complex than anticipated.
Did the Photon Split?
Let’s take a moment to clarify the concepts of photon splitting and combining. In everyday experiences, shining a single color of light through glass or reflecting it off a surface can result in photons splitting or combining, producing stunning colors. This phenomenon paints our universe in vibrant hues, akin to a legal LSD trip. However, such events are quite rare.
In reality, photons can split and combine under specific conditions. The medium through which light travels must adapt in response to the light itself. This reaction can generate a spectrum of colors from a single light source.
From a technical standpoint, the interactions of light we observe are linear, while photon combination and splitting are classified as nonlinear processes. Overcoming this nonlinearity typically necessitates either an extremely sensitive medium or a powerful light source, like a laser.
Though a mirror suddenly disappearing while a photon reflects may not initially seem nonlinear, upon closer examination, it is indeed a nonlinear event. However, our understanding of single photons interacting with mirrors might obscure this concept, as further elucidated below.
Source: arstechnica.com