Hi yall, I have a few questions in regards to EM radiation and photon density, or energy density; not sure what exactly the correct term would be here. (1) Anyway, first off, excluding the possibility that a black hole would form, is there anything that would limit EM radiation energy density to a certain amount? Because as far as I know, the Pauli Exclusion Principle doesnt apply to photons. I would think a black hole would eventually form(?) but besides that, is there anything that puts an upper limit on how many photons you can cram into a "box" so to speak? Or should I say is there a limit to energy density assuming the energy is only EM radiation? Take for instance a laser with a 1 meter aperture/diameter beam, would there ever come a point where you could not possibly increase the energy of the beam due to physical effects? Ignoring engineering difficulties and black holes of course.. (2) Also, what are the physical effects of very high radiation pressure? Like for example you have a box at which inside is full of EM radiation at Planck energy density, would it "feel" like air pressure, trying to burst apart? Or would the photons be fully "content" to stay at this density? Obviously "feel" and "content" do not apply to non-living things but thats the best wording I could think of. Thanks so much.