Light Without Paths: Relativity, Quantum Amplitudes, and the Relational Picture

Light is never observed in transit. We see it only at the moment it is emitted and at the moment it is absorbed, with no evidence of anything occurring in between. This simple fact, combined with the constancy of the speed of light, implies that a photon experiences zero proper time between emission and detection. Once this is taken seriously, the classical picture of a photon occupying intermediate positions or following definite paths becomes unnecessary. This paper presents a clear and accessible account of the double‑slit experiment based on this geometric insight. The interference pattern is not produced by a photon “exploring” multiple routes, but by the structure of the experimental setup itself. Each detection event is one sample drawn from a distribution fixed by the context—just as a single arrow on a target reflects, but does not define, the underlying distribution of possible hits. Using Feynman’s amplitude rules and a relational interpretation developed in earlier work, we show how the observed pattern arises without invoking motion through space or physical waves passing through both slits. The result is a simple, coherent picture that remains faithful to both relativity and quantum mechanics while being understandable to motivated high‑school students.