return to [6.2 Photon kinematics]

Figure 8. A photon O at the origin at t=0 is moving along the X axis in a positive direction. Events A and B occur x=ct distance-time away at coordinates (x,y,z) and (x,0,0) respectively. These events occur here-now, at any point of time, with photon O since they both occur at x=ct.