Like I said, any factual argument at all stating why you think the earth is not massive object crushed into a generally spherical shape by its own gravity, just like virtually every other massive, dense object in not just our own solar system but the entire observable universe. Why you don't think it's reasonable that the same gravity pulling the earth's own mass inward could not possibly also allow for things on the surface of the earth to also be pulled toward its center, creating an "up" and "down" that is relative to the earth's center rather than a flat plane.