both the sun and the moon appear larger when they are rising or sitting,although there is on real different in the distance they are form the earth. this perceptual phenomenon,known as the "moon illusion," has been studied over the years. various explanations, including the muscle strain for the person looking up and the comparison of the moon with other on the horizon that make it appear larger, have been disputed by scientists, but thus far there is on widely accepted explanation of the phenomenon