I found this at yahoo's fist page...
Robert Roy Britt
Senior Science Writer
SPACE.com Fri Jun 29, 2:00 PM ET
This weekend's full moon hangs lower in the sky than any other full moon of 2007, according to NASA, and it's a good time to be fooled.
When low on the horizon, the Moon can appear to be larger than when it's higher in the sky. It's all an illusion, scientists say, and it does not involve any enlarging effects of the atmosphere. Rather, it's all in your mind.
Here's how it works:
Our brains think things on the horizon are farther away than stuff overhead, because we're used to seeing overhead clouds that are close compared to those on the horizon. In the mind's eye, the sky is a flattened dome.
With this
dome as a reference, we expect something on the horizon (such as the moon) to be father, and because it is actually no farther than when overhead, our brains goof and imagine that it is larger.
Skeptical? You can test this from home.
When the moon first rises, hold something small like the eraser of a pencil at arms length and compare its size to the moon on the horizon. Do the same a couple hours later when the moon is higher. Or try this: Take a picture of the moon in both positions, then cut, paste and compare. Another trick: Make a tube from rolled-up paper so the opening is just slightly larger than the moon when it rises. Tape the tube so the size stays fixed, then check later to see if the moon has changed sizes.
Officially, the moon will be full Saturday June 30 at 9:49 a.m
Source:
http://news.yahoo.com/s/space/200706...trangeillusion