If the earth was rotating, the earth would be the guide not the sun.
Peace sNOVA
Just wanted to comment on this statement of yours ...
Once a moving light source relative to the object casting the shadow is determined we then go about using ourselves as reference markers ... unfortunately just as the Earth rotates, we do so and so does the shadow casting object ... the thing that remains out of sync with us is the sun ... or rather the angle of the light from the sun.
The movement needs to be there it does not matter if it comes from the sun or the earth but the object also needs to be there to cast the shadow.
a) Light source
b) Relative movement
These above will create a growing shadow ... but we need to be on the Earth to observe this ... If the relative difference in motion between the Earth and the Observer is 0 then we can say that the light moves ... if we are stationary with respect to the light source then we can say the Earth moves ... hence Geocentricity still has it's uses ...