Hi guys first post here so bare with me if I sound stupid...

Why are photons limited to light speed?

From my limited understanding the maximum speed of anything in the verse is the speed on which photons are measured at, I also understand anything with mass cannot be propelled up to this speed as it would need an infinite amount of energy as it reaches near to this speed. As photons have no mass they do not suffer from this setback.

I have read that it is possible to slow down photons by using heated caesium gas ?? Or other types, but upon leaving the gas chamber the photons are instantly moving at light speed again.

I have a theory but i'd like your input as it could sound a bit odd