As an outcome of his PhD thesis work, Richard Feynman and John Wheeler wrote a series of papers on how the kickback on an electron as it emits a photon can be modeled accurately as the result of an "advanced photon" traveling backwards in time and striking the electron. In their model, this peculiar back-from-the-future impact always occurs at the same moment as when the electron emits a more conventional "retarded photon" (don't look at me, I didn't come up with these names!) that then moves forward in time in a more conventional fashion.
The advanced photon is emitted by whatever electron eventually absorbs the retarded photon. That electron may be only a few femtoseconds away in the future. However, it could just as easily be billions of years in the future, such as when you point a laser towards an especially empty void in intergalactic space.
That last point has always intrigued me, since it seems to imply that the probability of emission of the photon is dependent on the distribution of matter in the universe across all of spacetime.
Imagine for example shining a laser out into a region of space for which the probability of its photons encountering future electrons is close to zero for the entire remaining history of the universe. According to the Feynman-Wheeler advanced-retarded photon pair model, the absence of a future electron to emit the advanced photon would seem to mean that no retarded photons could be emitted in that direction, and the laser would stop working!
So my question is this:
What is the resolution to the Feynman-Wheeler empty-space laser suppression paradox?
I assume by default that Feynman-Wheeler suppression does not exist, but I also have to admit I do not know that experimentally. I assume it does not exist because quantum probabilities alls seem to be very smooth, and Feynman-Wheeler suppression would violate that smoothness. It would instead make quantum uncertainty a function of how matter is distributed throughout spacetime.
But if Feynman-Wheeler suppression does not exist, why does it not exist?
That too would seem very strange, because it would seem to imply that some very peculiar invariant is at work in the universe as a whole. Specifically, it would seem to assert that no matter what direction you look in our very stringy, very clumpy universe full of intergalactic holes, dark energy, dark matter, invisible matter, and a tiny smattering of severely-clumped radiating matter, the probability of eventually encountering an electron is always exactly the same.
Really?? That kind of smoothness just does not strike me as an obvious invariant for the universe we actually observe. About the only idea I can even think of would be that this hypothetical electron smoothness invariant might be related to the idea of a holographic universe.
So: Is there some other resolution to the Feynman-Wheeler suppression paradox that does not (a) make quantum probabilities dependent on the distribution of matter throughout spacetime, or (b) require that the angular distribution of electrons from zero to infinity, from all points in all of space, always be smooth?