I haven't calculated the speed myself but, I doubt god intended you to measure it in MPH or that it's exactly 666. If it is, stranger things have definitely happened. Water is polar so it wants to stick to itself anyway and the acceleration due to gravity at aprox 9.8 m/s2 is pretty dam strong. The formulas used to calculate the size and shape of earth is trigonometry/geometry. There's a little bit of iteration involved to calculate orbit but it can easily be done by hand. Not super easy but nothing even close to the level of math I think you think it is. If your talking about quantum physics and shit, yes, there are a decent number of assumption that are questionable and may be wrong. I think a better example would be approaching a land mass with an mountain or some other landmark from sea. Island is out of sight then progressively comes into view from the top down. As for a specific, personal land based example, water tower and fort fincastle in nassau Bahamas. Idk, try to find a lighthouse on a peninsula or something and climb it.