What Limits Light's Speed?

Re:Puzzle of constant Lt speed regardless of source.Briefly,could the "vacuum" itself constrain "actual" Lt velocity to observed constant? While Ether discarded,certainly Lt velocity is measured in an "environment" ("vacuum" etc) that is NOT quantumly empty. Is it remotely possible that this "quantum environment" itself is the limiting factor? IE nothing can propagate within "it" (whether "it" is "vacuum","fabric of space", EM field etc) more rapidly than 300,000k/s? Perhaps Lts "native" speed is *really* 600,000k/s say. A jet flying 1k/s & sending 1 Lt beam forward & 1 beam rearward might actually measure 600,001k/s & 599,999k/s respectively, with no "quantum soup" or something akin to "permitivity" & "permeability"-LIMITING-the transmission speed to the observed maximum of 300,000k/s ??
- Ray (age 68)
Florida

it's very reasonable to think that electromagnetism will someday emerge from a deeper understanding of what makes up our spacetime vacuum. I'm not sure what it means to ask what the "native" speed of light would be elsewhere. If light is a form of excitation of this vacuum, it may not make sense to think about what it would have been in some other universe, with a different set of excitations, maybe a different spatial dimension, etc.

Mike W.

(published on 09/04/2017)