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article imageAn Event You Can't Miss: Saturday's Moon Illusion

By Tea Lulic     Jun 28, 2007 in Science
This Saturday night, June 30th, while looking at the sunset, you will notice a giant moon rising in the east. It will look like the Earth's moon, with all of the craters, but it will be inflated. What you might experience is Moon Illusion.
For many years, scientists have known that low-hanging moons look and feel unnaturally big. However, cameras do not see it - only our eyes do, creating a genuine illusion.
This week's full moon will hang lower in the sky than any other in 2007. Many would wonder what makes the moon look so low but if one considers the fact that the sun and the moon lie on opposite sides of the sky, he would be able to determine an answer to this question.
The summer solstice happened just last week - actually on June 21st. Thus, the sun is near its highest point in the northern skies. Logically, the full moon is going to be low.
While looking at the moonlight, the rays converge and form an image that is approximately 0.15mm wide in the back of your eye. High and low moons make the same image even though one is higher than the other. For years, scientists have tried to figure out why human brain thinks that one moon is larger than the other and they are still unsure of the answer.
In 1913, Mario Ponzo was the first one to discover an illustration of two identical bars across a pair of converging lines. The upper bar appeared wider because it spans a greater distance between the rails. This is known as "Ponzo Illusion."
Using this, some researchers believe that Moon Illusion is actually Ponzo's Illusion. The houses and trees in this case would be playing the role of Ponzo's converging lines. These objects actually trick your brain into believing that the moon is actually bigger than it is in reality.
However, every theory has a problem. Even the airline pilots experience Moon Illusion without any objects in the way. How is that possible?
Some researchers think it is the shape of the sky. Humans see the sky as this flattened dome - horizon is far away and zenith is nearby. This makes sense. Something that is further away will be perceived as smaller than something that is closer to one's eyes. Since people's eyes are trained in this way, it is not surprising that sometimes they view the moon as this large ball of light and sometimes as something that is so distant that it cannot be reached.
However, there are many explanations or theories for this phenomenon. But none of them really matter if you just want to see a beautiful, full moon and not think about the science behind it.
Here is a little hint for you: the best time to look is around moonrise - when the moon starts to peak in between the trees and houses, or over the mountain ridges.
And if you want to have fun with it, do this little activity: look at the moon directly, and then look at it through some kind of narrow opening. For example, you can make a cylinder out of a piece of paper, making sure that the side further from you is narrower, or by 'pinching' the moon between your thumb and forefinger. While doing this, ask yourself: Can I make an optical illusion vanish? After you have discovered an answer, share it in the comment section.
But please make sure you do not miss out on Saturday's Moon Illusion because of this activity. Enjoy!
This article was awarded TopScience piece by Digital Journal Editors as part of Digital Journal's Weekly Top Find Awards. Digital Journal staff review all articles published by Citizen Journalists every week, selecting the top stories for special recognition. To see a full report of all news and more details on this award, check out TopFinds.
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