
Originally Posted by
Capebuffalo
Newton's First Law - specifically, objects in motion tend to stay in motion.
Spherical Geometry of the Earth -
X degrees of longitude gives you more or less miles of distance at different latitudes,
objects are effectively confined to the surface by gravity (thickness of atmosphere is a tiny percentage of the Earth's radius).
Centripetal Acceleration - If the velocity is too high the object will try to increase its radius, if the velocity is too low the object will try to decrease its radius (fall). This one can be a little harder to get across to students, but fortunately it's not necessary for all cases.
Premise 2 is probably the easiest to get students to accept, since you can draw on a globe to demonstrate how an inch is 15 degrees here and 30 degrees there. And a simple comparison of the thickness of the troposphere to the size of the Earth completes it. 1 and 3 require at least a little science background or a few demonstrations to convince students of.