We aren't supposed to be able to detect the curve, because the world is supposed to be sooo hugeeeeee! But, we're still supposed to have a drop of around 4,000 miles over 6,000 miles. That's 2/3rds of a mile, over every mile or eight inches over every foot, then after about 6,000 miles, climb about 8 inches for every foot! The earth is supposed to be basically a sphere. Not a square or a rectangle, but a sphere.
Nobody observes it, but we're supposed to accept it, because if you knock a cup off a table, it falls down!
