MattPalmer1086 parent
Why would the absence of mass force something to travel at the maximum speed? I could understand it being able to travel at that speed; why would it always do so though?
Theoretically, a massless particle can move slower than light. But then it'll have zero energy and momentum, so it won't be able to interact with anything.
Thanks. The equations give the answer in the end, I found this explanation the best [1].
The only way to get a zero mass is if the energy is zero, or the velocity is c.
[1] https://profoundphysics.com/why-do-photons-have-no-mass-simp...