Super-computers running a million-million cycles a second take millions of seconds (months) to simulate not just what a photon does in a million-millionth of a second, but in a million-millionth of that (Wilczek, 2008) (p113). How can these tiniest bits of the universe with no known structures make such complex choices? The answer now proposed is that “a photon” is not a particle following a line path but a cloud of processing instances.
Feynman’s sum over histories method predicts how light goes from A to B by calculating all the paths, then choosing the one with the least action integral (Feynman et al., 1977) p26-7. It was accepted as a method because it works but not as a theory because a physical particle can’t do that. Like the rest of quantum theory, it was a physical impossibility that just happened to predict perfectly.
Now suppose that Feynman’s method works because it describes what actually happens. Photon instances do take all available paths and physical reality is decided down the line by the first one to trigger a server restart. The instance that happens to take the fastest path to a detector reincarnates as the photon in a physical event, making its path the one the photon took. The server restart makes all other instances disappear, like a clever magician removing the evidence of how a trick is done.
Indeed, how else could the law of least action arise? A photon particle can’t know in advance the best way to an unknown destination before it leaves, so the photon wave takes them all and the first to arrive restarts it in a physical event.
In a virtual reality, calculating and taking a path are the same thing. Knowing nothing in advance, the photon spreads instances down every path and the first to overload a detector becomes “the photon”. What reaches a detector by the fastest route isn’t a solitary particle magically knowing the best path in advance but a quantum ensemble that explores every path and disbands when the job is done.
It follows that every physical event comes from a myriad of quantum events. The quantum world tries every option and the physical world takes the best and drops the rest, so if this isn’t the best of all possible worlds, it isn’t for lack of trying.
The physical law of least action then derives from the quantum law of all action that:
Everything that can happen in physical reality does happen in quantum reality.
Gellman’s quantum totalitarian principle that “Whatever isn’t explicitly forbidden must happen” is equivalent to Feynman’s “Everything that can happen does happen“. Both imply that the photon takes every possible path and the instance that arrives first becomes “the path the photon took”. Yet again, quantum realism explains what physical realism cannot.