If the Earth is flat, and you live close to the "edge", there is a danger you could walk off the edge? If someone walked off the edge, would gravity pull them back and they are now walking around on the bottom side of the disk? Taking this a step further, wouldn't all kinds of stuff like rocks, water, dirt, trees, etc. fall off the edge, then be collected on the underside? If that happened, over millions of years, wouldn't the Earth begin to take on a more spherical shape as things fell off the and became stuck on the other side?