With geocentric gravity, you can have a spherical Earth. Not sure from memory when this was introduced, but probably BC. This then raises the question of how the outer "spheres" stay up there. If gravitational force diminished at a rate higher than inverse-square (as the Strong Nuclear Force actually does), then you can handwave away most of that problem. With this alternate physics, human-powered flight could be practical if you could only get far enough from the ground, which is a fun thing to think about.