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How can a photon have velocity if?
It has no temporal velocity? By my understanding of Einstein's four-vector, any particle with a spatial velocity c must have temporal velocity 0. But if temporal velocity is 0, the regular velocity (d/t) must be infinity. So, on a Feynman diagram, a photon should just be a horizontal line (parallel to the x axis, perpendicular to the t axis). But it seems to take a certain amount of time to get between two spatial points. Can someone explain to me how this makes sense?
but "f", in this case, is a very big number, isn't it?
1 Answer
- Dr. RLv 71 decade agoFavorite Answer
Keep in mind that if you have two functions of x, say, f and g, the ratio f/g does not necessarily approach infinity as x approaches 0 just because g approaches 0 as x approaches 0, as you assume. If f also approaches 0 there too, you have to take the limit using L'Hopital's Rule.