If a photon does not experience time and exists in its full trajectory at a given instant, how does it “perceive” a body moving to cut its path?

Question

OK maybe ELI12 would do.

In: Physics

Answer 1

In this way of envisioning the universe from the point of view of the photon, “movement” does not exist because time doesn’t really have meaning. The object that intersects its path can be visualized as a 3D object smeared through the 4th dimension, and that smear at some point intersects the ray of the photon in the 4th dimension.

To make an analogy, imagine you are looking at a road that crosses a railroad line. How does the road “see the rail line move and interact with it”? It doesn’t, they exist simultaneously with a particular point of intersection.