DiameterThe diameter of the ball is the same as its height. The radius is the measurment from the center to the
surface, this is half of the diameter.
CircumferenceThis is the measurement around the outside of the ball at the widest point. This would be measured with
a tape measure, similar to taking a waist measurement.
Surface areaThis is the area on the outside of the ball. This is usefull to know to have an idea of how much paint
it will take to coat a sphere.