🚀 go-pugleaf

In article <sehari.713428190@vincent1.iastate.edu>, sehari@iastate.edu (Babak Sehari) writes...
> 
>In order for something "hitting" another thing, it should have defined size
>and defined location.  Now could you tell us, how big is a photon or where

This is completely untrue.  You can, in a completely well defined way, 
determine the probability for an electron-photon interaction without 
any defined "size" or "location" for either particle.  Loosely speaking,
you integrate over all possible interation points weighted by the appropriate
probability density distributions for both particles.  A great place to 
read about this stuff is Sakurai's _Advanced Quantum Mechanics_.  

>exactly is located.  Since, we know the velocity of photon very accurately,
>we can not tell it's position to begin with.  Neither, a photon has a size.
>A photon might be as big as the whole solar system, or as small as an atom.
>What we have here is the interaction with electron and interaction with
>another photon.  A proton's interaction with another photon causes
>destructive and/or constructive interference.

No.  The interference pattern you see is not the result of any interaction
between the photons in the beam.  A perfectly non-interacting beam of photons
would still produce exactly the same interference pattern.  "Interaction"
implies that the momentum or position of one particle is affected by another
particle.  No such thing is happening when you form an interference pattern
by, for example, splitting a beam in a classic interferometer setup.  To
understand clearly what exactly *is* happening requires a bit of quantum
mechanics.  I am pressed for time, so I will leave those details for 
someone else.

-Scott

--------------------
Scott I. Chase			"The question seems to be of such a character
SICHASE@CSA2.LBL.GOV		that if I should come to life after my death
				and some mathematician were to tell me that it
				had been definitely settled, I think I would
				immediately drop dead again."      - Vandiver