Why the moon looks bigger on the horizon
The moon appears to be much larger when it is near the horizon than it does when it is high in the sky. Appearances are not deceiving; the moon is larger when it is low in the sky. The moon is a ball of negative density gas. Just as positive density gas expands when the pressure is less, so negative density gas contracts when the pressure is less. As we know, the density and pressure of the atmosphere falls off with altitude. When the moon is low in the sky the pressure is greater so the moon expands. When the moon is high in the sky pressure is less so the moon contracts. Thought you'd like to know.
This page was last updated May 4, 2003.