Photons can "stack" without any problems. Your box would have a discrete spectrum of allowed energies (corresponding to standing waves in the box), similar to a laser. For each allowed frequency, you can have an arbitrary amount of photons inside.so small that only a single photon could tightly fit inside
A thought experiment is a mental exercise or hypothetical scenario used to explore and test ideas, theories, or concepts. It is often used in scientific and philosophical discussions to gain a deeper understanding of a concept or to challenge existing beliefs.
In the thought experiment, the light bounces back and forth between two parallel mirrors, theoretically creating an infinite number of reflections. This creates a continuous loop of light, with the intensity decreasing with each reflection due to some energy being absorbed by the mirrors.
The purpose of the thought experiment is to explore the concept of infinity and how it relates to the behavior of light. It also challenges our understanding of how light behaves and raises questions about the nature of reality.
While the mirrored box thought experiment is purely hypothetical, similar concepts have been applied in real-life situations. For example, fiber optics use the principle of light bouncing back and forth between mirrors to transmit information.
One criticism is that the experiment relies on idealized conditions and does not take into account factors such as imperfections in the mirrors or the presence of other particles that could affect the behavior of light. It is also argued that the thought experiment does not provide any new insights or testable hypotheses, making it more of a philosophical exercise than a scientific one.