I don’t know why the speed of light has the specific value it has for matter observers, but I think I know its true meaning. The speed of light is a real “speed limit” in the universe, because it represents “instantaneity” at the same time. Any phenomena or process that appears to be developing at the speed of light to us takes no space or time at all from its own perspective.
Time dilation and length contraction are so extreme at the speed of light that they break our notion of spacetime. Extreme SR effects stretch any interval to that of a single instant, and any length to that of a single point. Without spacetime, any massless particle at c feels at the beginning and the end of its journey at once. Photons (or any other massless quanta) don’t experience our spacetime intervals. What we picture as emission-flight-detection processes are instantaneous point-like events for them.
This fact then reveals an important duality for any process taking place in the universe:
c speed = infinite speed
This means that it doesn’t matter there’s a speed limit in the universe because, for all purposes, things that travel at c feel they’re instantaneous. They traverse any distance in no time (for themselves) so they’re, effectively, teleporting instantly at infinite speed.
c speed is just the incredibly distorted way in which we perceive instantaneity. It is only an artifact, caused by our inability to reach the massless perspective.
So any quantum object at the speed of light is at the same time a bridge between two spacetime points, behaving like a wormhole that connects them in no time (for itself). This way, it doesn’t matter if two entangled particles travelled millions of lightyears in opposite directions starting from a common point, because each carrier still feels linked to the entanglement event wherever/whenever it gets detected. For them, emission-flight-detection is just the same thing.
This “relativity of speed” or “relativity of spacetime” (that what appears as a process to us is a single event for them) can explain all QM weirdness (entanglement, nondeterminism, wave/particle duality, wave function collapse, Bell’s theorem, faster than light communication, EPR paradox, Scrhödinger’s cat experiment, double-slit experiment, delayed choice experiment…)
I talk in more detail about these topics here:
