You've probably noticed that the moon looks a lot bigger when it's near the horizon than when it's high up in the sky. What you probably don't know is that there is, as of today, in the year 2006, no scientific consensus as to why this is so!
There are many hypotheses, of course. They include the idea that we have buildings and trees to compare the moon to at the horizon so it looks relatively bigger (but the illusion persists even on flat, featureless terrain), the idea that there's some sort of atmospheric effect involved (there isn't), the idea that we have a mental map of the sky dome that's flatter than it really is so the same angle translates to a bigger object (maybe part of the explanation, but no real evidence of that), etc. etc. etc.
Here's a page that argues in favor of an "oculomotor micropsia" explanation, that our eyes focus closer when we look up, because there are no visual cues to focus far, so the moon looks bigger because of that. It seems pretty convincing, but here's a page with lots of info on different explanations for the Moon Illusion, which also says that ocolomotor micropsia doesn't make a big enough difference to fully account for the moon illusion. It concludes that we still just don't really know why it happens.
I'm just amazed that something that seems so simple, like it should be basic math or physics, but it actually turns out to be an unsolved mystery!
I almost forgot to add my postly image! Well, here's a picture of a bunch of zebras:
I found it from the Cellar Image of the Day, where there's more information about it, namely, that zebra use their stripes not to blend in with trees so much as to blend in with each other. Apparently, predators have a hard time tracking individual zebras; they just see a big mess of stripes. And who can blame them!
