> with the special highlighting of massless particles which are further constrained to follow null geodesics. Only to an approximation. Photons generate gravit

> with the special highlighting of massless particles which are further constrained to follow null geodesics. Only to an approximation. Photons generate gravitational fields, and the planets they travel near are attracted to the photons (not much obviously). (See: Kugelblitz) Gravity does not treat photons specially, the rules are the same as for other particles. For extra credit imagine a Kugelblitz traveling by at light speed - it's moving so fast, it doesn't have time to add any mass. Yet, mass transited inside the event horizon of this object.