Every year I am asked to answer what things look like when traveling at the
speed of light. I know that is prohibited. But today the question took the
form of " how would one photon describe another photon?" I know that
Einstein tried to imagine what an em wave would look like if traveling with
it, but I don't know/understand what he decided he saw.
I feel inadequate in not knowing about this or being able to satisfy the
curiosity of my students. Can anyone help me out?