Re: Researching an Idea


MackTuesday wrote:
> Photons can't propagate through vacuum? Do you have that in writing
> somewhere? It's true that you can't detect a photon unless it
> interacts with something, but otherwise the photon cheerfully
> propagates unhindered.

I don't have any reference, it was something I read ages ago. My
understanding is that it has to do with QED. Photons don't
"propagate", they just interact with electrons. Each interaction has a
probability and the QED formulas are a way to add them all up. For
example, one history might be a photon is emitted by electron 1 at
position and time 1, and then is absorbed by electron 2 at position and
time 2, what it does between the two times is not defined. When you do
the summing, you get the standard, photons moving at light speed have
the highest probability.

However, if there aren't actually any electrons "in that direction",
then the histories of photons going in that direction can't exist, so
there is a probability of zero for some of your histories.

Photons can propagate through a vacumn but only if there is an electron
to receive them on the other side. This can be an arbitrary amount of
time into the future. If the universe is very large, then for any
given direction, the path of the photon will intercept an electron, so
there is no directional asymmetry in the propagation of light. Also,
as I said maybe the quatum vacumn might also allow photons to propagate
anyway, i.e. the photon is not absorbed by an electron but interacts as
part of some virtual particle exchange. I think a real physist is
probably needed here.

.

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