Quote Originally Posted by atpollard View Post
[the real trick is to adjust for rotation]
Ooooh, yeah - any modest-speed projectile would have to account for coriolis effects. I'm thinking the equivalent of rhumb lines could be correction curves for artillery or archery.

More low-tech possibilities include enhanced ease of flying ('gravity' falling off with height, to zero at centerline) and secrecy-via-fog (otherwise, given adequate atmospheric clarity, everybody can see all the territory). Astronomy could be restricted to the underground miners who accessed the 'windows in the bottom of the world'... and would be pretty useless for navigation.