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57 °F Forecast | Road Cams Sunday, September 19, 2004 Today's News | Classifieds | Autos | Homes | Jobs | Tempo | Health | Community | Home Delivery SECTIONS Home Page Local News Sports Business Obituaries Life Opinion - Politics Tempo AP News Weather Classified Archives Site Map SPECIAL SECTIONS Since We Asked Outdoor Journal How To Guide Wellness Connection Readers' Choice Real Estate Showcase Joy Magazine Homelife Magazine Wedding Guide Rogue Valley's Finest EXTRA Newspaper in Education Personals Movie Times TV Times E The People MARKETPLACE Find a Car Find a Home Find a Job Classifieds Place an ad eSouthernOregon Automotive Communities Entertainment Publications Recreation Calendar CUSTOMER SERVICE Frequent Questions Advertising Information Home Delivery Employment Contact Us Media Kit Network Affiliate Oregon Road Conditions & Cams Email Story to a Friend August 31, 2004 Since you asked Moon size is merely illusion Last evening as I watched the full moon rise over the eastern horizon it appeared close and super-large. A few hours later as it moved overhead it appeared smaller and farther away. What causes this phenomenon? — Jim M., Grants Pass We put a man on the moon, Jim, but we still can’t tell you why it looks so big on the horizon. The fact is, the moon remains exactly the same size as it moves through the night sky. You can verify this by holding a ruler at arm’s length to measure the moon on the horizon and measuring again when it’s high in the sky. The lunar disc will occupy the same space on your ruler. As for why the moon appears so much larger on the horizon, there are several theories. Most involve some variation on the notion that our brains "translate" (perhaps "mangle" would be a better term) what our eyes actually see to make us think the moon looks larger on the horizon. Apparently, these mental gymnastics are connected to the brain’s experience with interpreting the size of objects at varying distances. Advertisement The moon’s in a peculiar place, when you think about it. Compared to objects in this world, it’s huge — 4,000 miles across. But it’s also distant — 240,000 miles away. It seems our eyes and brains just can’t quite decide how big the moon really is. Seeing trees and other familiar objects that we "know" to be large as the moon rises behind them could make it appear larger. Or at least that’s one school of thought. You can unfool your brain by changing your frame of reference to the rising moon. Try looking at the horizon upside down, or standing on your head, or looking at the rising moon through a toilet tissue tube that blocks out the surrounding detail. The moon probably won’t look as big. Here’s another example of how our eyes fool us. Draw two horizontal lines about 2.5 inches long, about 5 inches apart on a sheet of paper. Then draw in a pair of lines that look like railroad tracks converging at the horizon. Make sure the "tracks" are wide enough at the bottom for the lower horizontal line to fall inside them, and narrow enough that they cross the upper horizontal line. If you do this right, the upper line will suddenly appear smaller than the lower one. You say you’re no artist? Fire up your computer and tell your Web browser to look for something called a "Ponzo illusion." Mail Tribune Home Local News | Sports | Business | Obituaries | Life Opinion - Politics | AP News | Archives | Site Map E Southern Oregon | Classified Copyright © 1997-2004 Mail Tribune. All rights reserved. Privacy Policy | Terms & Conditions Website Feedback ADVERTISERS A D V E R T I S E R S SPECIAL SECTIONS Auto Finder Job Finder Home Finder Joy Magazine Homelife Magazine Tempo Readers' Choice Real Estate Showcase Since We Asked Outdoor Journal Moving to Southern Oregon? Volunteer Opportunities