Why don't ordinary photons spontaneously collapse into black holes? You should get a singularity if the energy density in any region of space is high enough. But you can pick an inertial reference frame such that any given photon has arbitrarily high frequency (and thus energy) due to blueshift. Since any inertial reference frame is as valid as any other due to relativity, why don't all photons collapse under their own weight?
Why don't ordinary photons spontaneously collapse into black holes?
How do you know that ordinary photons aren't black holes?
This thread is for asking any questions that might seem obvious, tangential, silly or what-have-you. Don't be shy, everyone has holes in their knowledge, though the fewer and the smaller we can make them, the better.
Please be respectful of other people's admitting ignorance and don't mock them for it, as they're doing a noble thing.