Moon Illusion

In addition to the illusions involving the apparent backwards movement of mars and the humanoid face in Cydonia, there is another illusion in space a little closer to home: the moon illusion. The Moon illusion is a visual illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. The moon seems larger in angular size when it is near the horizon than when it is high in the sky. Some people judge it to be as much as twice as large, but the average estimate is 50% to 75% larger.This optical illusion can also occur with the Sun and star constellations.

There are some simple ways to prove that the moon is not actually changing size including photographs of the moon at the horizon and higher up reveal that they are exactly the same size (if taken with the same camera settings).

Another way of demonstrating that the effect is an illusion is to hold a small coin at arm's length with one eye closed, positioning it next to the seemingly large moon. When the Moon is higher in the sky positioning the same coin near the moon will reveal no change in size.

The moon illusion occurs primarily through visual angle illusions. Click here for a more in depth discussion with multiple approaches to explaining this phenomenon.