About Photons

 Photons are massless or nearly massless particle/waves (bosons) force carriers of an electromagnetic field. Their speed seems fairly certain. Relativity and the problem of simultaneity of measurements in different location present issues for calculating times apparently. Sub-atomic particle-waves are slowed down to less than light speed in the Higgs field and thus have a third dimension of mass. Without the Higgs field mass would not exist, and energy like photons I believe would be two-dimensional and flat like a communion wafer. It is all interesting stuff to learn about- especially as regards relativity and uncertainty. The books 'What is Real'  by Adam Becker and 'Mass' by Jim Baggot are good easy to read works that go pretty deep into quantum topics. There is another book that I read a few years ago named 'Faster Than the Speed of Light' by Joao Magueijo that was an interesting speculation on variable speed of light theory. I liked that book and for a while thought it might be so. If space expands quickly it might be possible for a field to expand with it including an electromagnetic field or a Higgs Field or unified field and then if particle-waves existed in it they too might be travelling faster than light usually does. I guess though that speed is simply relative to other objects or particle-waves while in-themselves they are motionless.

Photons and other massless particles seem to have a basic speed of just being. That initial, basic speed of just existing-in-themselves is faster than particles with mass that are all slower than light and massless particles because they are all slowed by the Higgs Field to sub-light speed picking up that third dimension characteristic of mass that massless particles of two-dimensions may not have.

Plainly there appears to be faster than light sharing of information among entangled particle waves. That apparent phenomenon could be an endemic characteristic of waves and the  Schrödinger equation or wave function. Maybe it is also related to dimensional shortcuts. Interestingly gravity also travels at the speed of light. Perhaps that is a property related to the fact of nothing traveling faster than massless particles like photons and neutrinos just being.

https://www.sciencedirect.com/science/article/pii/S2211379719330943