>>18153555The curvature is curvature as from a point of observation not affected by the earth's gravity, when you're on the curvature it is a level. It's about frames of reference. Imagine a very very very long flexible spirit level going across thousand of miles, accounting for elevation and all that, it will be able to be perfectly balanced. However from the perspective of beyond that, if the level is created in the first place by the gravity of a sphere then the thousands of miles of flexible spirit level will look curved. You have to be able to simultaneously account for two different frames of reference and recognise which variables are relevant when attempting to define which is more objective than the other
