@LCC1204@jpvanhoy@truthache68 Or other basic geometric relationships, like finding the height of a tree by knowing your distance from its base, and the angle from that position to the top.
@LCC1204@jpvanhoy@truthache68 I'm talking about basics like the size an object's angular size will change with distance, or how an object across a planar surface will remain at eye level with distance if it starts at eye level and moves parallel to that surface.
@LCC1204@jpvanhoy@truthache68 But you can measure the form of the Earth through geometric principles we can all agree upon. And gravity has been tested extensively.