Tonight as the sun is setting, look to the eastern horizon to see the moon rising. This full moon is known as the “Solstice Moon” and if it looks bigger to you, don’t panic, the moon is not suddenly hurtling toward Earth. This effect is known as the Moon Illusion and astronomers have been wondering about it for a long time.
Photographs taken of the Solstice Moon rising show that the illusion only happens to human eyes, not cameras. (See the example here.) And the theory of why it happens is similar to the Ponzo Illusion. (No relation to the Ponzi Scheme.)
The sun sets in Los Angeles at 8:08pm tonight, with the moon rising about 40 minutes later.
Follow me after the break for more on the Moon Illusion and tonight’s beauty.
The Ponzo Illusion was “discovered in 1913 by Mario Ponzo, who drew two identical bars across a pair of converging lines…The upper yellow bar looks wider because it spans a greater apparent distance between the rails.”
From the NASA page:
Some researchers believe that the Moon Illusion is Ponzo’s Illusion, with trees and houses playing the role of Ponzo’s converging lines. Foreground objects trick your brain into thinking the Moon is bigger than it really is.
But there’s a problem: Airline pilots flying at very high altitudes sometimes experience the Moon Illusion without any objects in the foreground. What tricks their eyes?
Maybe it’s the shape of the sky. Humans perceive the sky as a flattened dome, with the zenith nearby and the horizon far away. It makes sense; birds flying overhead are closer than birds on the horizon. When the moon is near the horizon, your brain, trained by watching birds (and clouds and airplanes), miscalculates the Moon’s true distance and size.
No matter what the explanation, the man in the moon shows his full face tonight. Say hello if you get the chance.
For much more info, go to NASA’s Moon Illusion page.
(Moon image used under a CC license and is credited to Luc Viatour. Ponzo Illusion created by NASA and is in the public domain.)