1. Time seems to have a 'smallest step' -- the Planck time unit. 2. A photon travels at c. 3. When you get closer to c, time dilates causing your passage in time to get slower compared to the rest frame. And now... If a photon is emitted at point A and absorbed at point B, then from the point of view of that photon, how much time has passed? An eternity? None at all? It all happened at the same time? This one's been bugging me for a long time now.