This is a question from an interested amateur. Math welcome (as I or another may investigate it some day) but don't expect me to understand it in your answer.
Consider a star emitting light. In order to talk about it simply, think of a point light source, and ignore spatial perturbations (for the sake of phrasing the question). At at time t, the light emitted at a single instant at now-t forms a sphere at a distance from the source. What is the density of photons in the surface of that sphere?
Perhaps the reply is that the energy is traveling as a wave, but I understand light energy is quantized - that is, the energy has no representation described by infinitesimals, but will be in minimum quantities.
How much must the sphere expand so that there are gaps in the image when sampled at different locations on the 'instant-sphere' image?
Or, is there an explanation as to why the energy is quantized, yet can manifest at any separation (due to distance) despite the energy density falling below the quantization when the sphere is of sufficient size? What if the source is a candle? Is the original source always sufficient to 'map' adequate photons to any sphere that may be created in the dimensions of our universe?
Are there objects we cannot see because they are so far away (or dim) that we are 'in-between' the photons that form their expanding image?
Of course, I may simply not understand, but the explanation would be welcome.