Stealth Pilot writes:

the reference I gave gives details of some original work by Fresnel
which proposed that light passing beside a gravitational mass should
be bent slightly by the mass and behind the body there should be a
bright spot. this seems to me to be the explanation for the absense of
the shadow. the mass of the aircraft acts as a gravitational lens and
this causes the bright spot.

It's much simpler than that. The shadow is so blurry at altitude that you
cannot see it, but it is still there, and it is almost exactly the same size
that it would be on the ground. Gravitational lensing is not significant for
an object with the mass of an airplane (but it works for the sun, which is
considerably larger).

The bright spot comes from direct reflection of the sun behind you.

And pilots are not the only people who see these phenomena. Anyone riding in
a plane can see them, pilot or not. Indeed, the plane isn't necessary either,
as they can be seen from hilltops, mountaintops, and even from the roof of a
tall building.

the reason I asked the question was to point out that simulators work
on a simplified model of the reality that real pilots are exposed to.
people like mxsmanic seem utterly oblivious to the fact that their
exposure to the simulator will never give them competent knowledge
because all they are exposed to is a simplified model of reality. it
is only exposure to the actual reality that will allow you to achieve
competent knowledge.

Simulators simulate what is important; they don't simulate what isn't.
Simulating a few rare optical phenomena is so unimportant that it would be a
waste of code to simulate it.

if simulators dont get something as simple as the aircraft's shadow
right can you trust that anything else they show you is right?

Yes.

Microsoft Flight Simulator actually has better visuals than some
multimillion-dollar simulators. Does that mean that the latter are "bad"
simulators? No. It just means that these latter simulators emphasize other
aspects of the simulation; the relatively primitive visuals are there because
the simulator is not normally used for VFR simulation, and photorealistic
visuals are very expensive. You can bet that these expensive full-motion
simulators don't normally simulate heiligenschein, glories, rainbows, or other
minor phenomena, either.