I've done a simple experiment proving the Earth's nearly spherical shape and size.
I've calculated the Earth's circumference by observing and measuring the North Star's angle of view from my horizon with a clinometer at 46 degrees latitude and then comparing Polaris' angle of view from my horizon at 43 degrees latitude. Using an odometer, I measured the 200 miles of distance I traveled north to south on I-29 between 46 and 43 degrees latitude.
I then took the 200 miles distance difference and divided it by the 3 degrees latitude difference and calculated 66.666 miles per 1 degree of distance. Then I multiplied 66.666 miles * 360 to calculate the Earth's circumference at 24,000 miles.
Maybe if educators and their students would do fun and interesting scientific projects similar to what I've described above, then they could measure and see for themselves that the Earth is nearly a perfect sphere with a circumference of around 24,000 miles instead of flat.
Has any other RF members here other than me actually measured and calculated the Earth's circumference. If so, what were the results of your observation, measurement, and calculation for the Earth's circumference size?