The particles (or whatever you want to call them) that makes up light, exist
everywhere at all times and can pass right through matter (this is the key to
my explanation). These particles are invisible (and I guess not yet detectable
by conventional means) and travel in all directions at speed C. Visible light
(or detectable light) on the other hand only becomes visible when these
particles are charged and are only visible from the point where they are
charged and in the direction of the charge up until a point were they lose
thier charge (or something to that affect). Although these particles can pass
through matter, it's charge can only be sustained through certain types of
matter (like air, water, glass, etc.), which is why light cannot be seen going
through a wall, unless a very strong charge is applied (as in a high powered
laser) in which case it burns through the wall. To go back to the person on
the train example, the reason that the light is observed to be the same speed
in all frames, is because it is passing right through the train (and everything
else for that matter,) and is only visible at the point where the laser pen (or
whatever) was activated.
Does this make this?
Thanks again for your responses,
-= Russ =-