I think you’re talking about null vectors/geodesics, which define light, which from the viewpoint of any external observer does move through spacetime. https:/

I think you’re talking about null vectors/geodesics, which define light, which from the viewpoint of any external observer does move through spacetime. https://physics.stackexchange.com/questions/23058/why-is-light-described-by-a-null-geodesic https://physics.stackexchange.com/questions/23058/why-is-lig... https://physics.stackexchange.com/questions/188859/what-is-a-null-geodesic https://physics.stackexchange.com/questions/188859/what-is-a... Remember that it’s deceptive to imagine things like the POV of a photon, and better to think in the usual terms of external observation.