Every particle has a life line (segment). Light particle's life line segment is perpendicular to the time axis, jumping across empty space (from birth/emission

Every particle has a life line (segment). Light particle's life line segment is perpendicular to the time axis, jumping across empty space (from birth/emission to death/absorption) at one constant time. If an atom emits an alpha particle (helium atom) and gamma particle (photon) at the same time, the alpha particle moves through space while its proper time changes (its "imaginary clock" ticks), whereas the gamma particle instantly arrives at its destination somewhere else in the Universe without experiencing any change in time, absorbed by another particle. Since light has no mass, it has no impact on spacetime geometry, so it only exists at emission and absorption. There is no way to detect or affect it between those to moments in its life, so it makes sense to consider them exactly one moment. Lights line segment is a "dotted line" the line segment (exclusive of endpoints) between emission and absorption does not really represent any part of our Universe; it's purely virtual. The only way to affect a photon is to plan ahead and set up an apparatus before it is born. Once the photon exists (relative to any observer), it's already gone (absorbed) by whatever first observed it. (And nothing else can directly observe it. All of us can bounce lots of stuff off the moon to observe it, but only one person can bounce only one thing off a photon , which kills it)