In article <ci7s7i$4i0$[Only registered users see links. ]>,
"Richard" <[Only registered users see links. ]> wrote:
The problem here is you are mixing two inherently incompatible models of
light. First, there is the classical model which describes light in
terms of waves, rays etc. In this model, it makes sense to describe the
path of light as a straight line (your linear paths).
The other model is quantum electrodynamics (QED) which describes light
as photons. All particles in quantum theory exhibit both classical wave
behavior and classical particle behavior. And in QED, a claim photons
"travel in straight lines" is too simplistic to be valid.
For most applications in physics including relativity, the classical
model of light as waves and rays is adequate and much simpler than QED.
Consequently, this is generally the preferred model.
If you are interested in learning more of QED a good place to start
would be Feynman's book QED: The Strange Theory of Light and Matter.
This book covers the basic concepts without requiring an extensive
mathematical background. It is available in paperback at modest cost
from the usual places such as amazon.com
I've snipped the remainder of your questions since they also would be
addressed by a better understanding of QED.