How Gravity Works on Flat Earth

Long before the theory of gravity was a glimmer in Newton's imagination, the natural physics of density and buoyancy already perfectly explained why apples fall down. Quite simply, objects fall or rise based on their relative density to the medium surrounding them. Apples fall because they are denser than the air, while helium balloons rise because they are lighter - no 'gravity' necessary. This is why raindrops fall down through the air and air-bubbles rise up through water! Everything seeks its relative density and rises or falls until settling accordingly. This is why a tiny pebble sinks to the bottom of the ocean, but gigantic cruise-ships and aircraft carriers stay afloat on the surface, because even though a pebble is so small, its mass relative to its volume (its density) is more than water, so it sinks, and even though a cruise-ship is so large, its mass relative to its volume is less than water, so it floats.