Moon illusion

The moon illusion is the idea that the moon looks bigger when it is closer to the horizon than when it is high in the sky. This is an illusion because the moon does not actually change size. Instead, the brain just visualizes the moon differently depending on how close it is to nearby objects in the sky, such as trees or buildings. The brain also likes to compare objects, so when there are fewer trees or objects in the sky, the moon looks bigger because there's nothing to compare it to.