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Re: [Phys-L] Each ray travels "as if it knew" all values of t=t1+t2




On 2014, Apr 13, , at 12:54, Ken Caviness <caviness@southern.edu> wrote:

Treating it in a quantum, "sum over all histories" way:

The light acts as if it follows all paths from point A to point B, but most of those paths cancel out: the wave arriving by almost every path interferes destructively with the wave arriving via some other route. The minimum time path, however, can't cancel out: the wave arriving that way arrives first, before any other candidate for interference. So the light wave traveling along the minimal time path is the one that actually occurs, the one that is actually observed.

Perhaps someone with a stronger background in quantum electrodynamics could vet that paragraph, but I believe it to be basically correct, and it obviates any need to assume light rays that somehow "know" before they select a path which one will end up being the least-time path.

KC


Sounds like what I read in one of Feynman’s pop books. {likely QED}

bc doesn't know anything more than what he remembers from "that" book.