Moon Illusion

On the evening of June 18, 2008, the moon appeared to many to be exceptionally large and close to Earth. Astronomers say this "moon illusion" normally happens a few days before the beginning of the summer solstice.

Fast Facts

1. Known as "Moon Illusion" or "Solstice Moon"
2. In 2008, best viewed on the night of June 18
3. Illusion often precedes the summer solstice¹
4. When the sun is high on the horizon, the moon appears lower¹
5. The low-hanging solstice moon may appear much brighter than normal as well
6. One theory is that objects in the foreground—like trees or houses—make the moon appear even bigger to the eye¹
7. Theory commonly known as the Ponzo Illusion¹
8. Discovered by Italian psychologist Mario Ponzo¹ in 1913
9. Next moon illusion may not happen for five or six years²

Quote

"...the sun and full moon are like kids on a seesaw; when one is high, the other is low. This week's high solstice sun gives us a low, horizon-hugging moon and a strong moon illusion."—NASA¹

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