"By the way, what I have just outlined is what I call a "physicist's history of physics," which is never correct. What I am telling you is a sort of conventionalized myth-story that the physicists tell to their students, and those students tell to their students, and is not necessarily related to the"
"P67.the length is about 0.192(0.98*0.2*0.98) which i approximated as 0.2 in the first lecture"
"P103 Once a photon has been emitted, there is no further turning of the arrow as a photon goes from one point to another in space-time."