In L3 T3 you write that something moving at c “does not experience time”. I find this interesting and have heard various versions of this statement, but I have a problem with its meaning.
Since c is a finite speed, a photon is at position x_1 at time t_1, and at x_2 at t_2, even if a photon is also a wave packet and not just a point particle. We can say that a photon’s experience is different at t_1 compared to t_2. That has to mean it “experiences time”. … No?