Why does the moon appear larger near the horizon?

This is actually an optical illusion known as the moon illusion. The moon is not physically larger near the horizon, and photographs confirm it measures the same angular size regardless of its position in the sky. The brain is tricked because when the moon is near the horizon, it appears alongside familiar reference points like trees, buildings, and terrain, which causes the visual system to perceive it as farther away. Since the brain registers it as distant but still forming a large image on the retina, it interprets the object as enormous. When the moon is high overhead, those cues disappear and the brain judges it as closer and therefore smaller. Covering the moon with your thumb eliminates the illusion entirely.