tmh@ihldt.UUCP (10/21/83)
It seems to me that back when I was getting my B.A. that it was explained to me as an optical illusion similar to the one with the two lines with arrows pointing in opposite directions. The size determiner seems to be the average size house (i.e. thing that interupts your horizon) in your neighborhood. The story in class went; some Anthropoplgists first noticed this when they were with some Afican desert dwellers and were remarking on how big the moon was. The natives remarked that they were crazy since the moon never changed size. The natives lived in small huts and there were virtually no interuptions on the horizon. It just go to show that to people who live in grass huts the moon is a harsh mistress?!?, Tom Harris
rob@lzmi.UUCP (10/21/83)
I believe the reason the moon appears larger when it is closer to the horizon is that at that angle, there is more atmosphere between you and the moon, which acts as a sort of magnifying glass. (similar to the way a pencil in a glass of water appears distorted...) ...........rob
walsh@ihuxi.UUCP (10/24/83)
Sorry Rob, no way. If you look at photos of the moon in time lapse from horizon to zenith, it is exactly the same size in each photo. The reason is, as I and a few other people have explained, the reference to the horizon creates an optical illusion (i.e., the moon next to a tree looks much larger than it looks when overhead). The difference between the atmosphere at the horizon and the atmosphere overhead is not sufficient enough to bend light to that degree.
mmt@dciem.UUCP (Martin Taylor) (10/24/83)
The Moon Illusion has a venerable history, with theories going back to Plato. Some of what has been written to the net is now accepted as giving part of the illusion, but the atmospheric idea isn't one of them. The effect of the atmosphere is to squash the shape top to bottom into an ellipse, not to magnify it in any dimension. For a partial discussion, see Scientific American about 10 years ago (look in an index volume in the library). The illusion has many parts, and I can't remember most of them. Martin Taylor
eric@apollo.UUCP (Eric Peters) (10/25/83)
As to why the moon looks bigger when it's near the horizon; it can't be simple atmospheric distortion: 1) When I take a picture of the moon near the horizon, it doesn't look bigger than normal in the resulting picture (I measured it); and 2) When I see the risen moon just over a hill (i.e. at an angle above the horizon where it usually doesn't look bigger) then it DOES look bigger. Could it be a subjective effect, similar to the sky appearing to be a flattened dome? (Ask someone to point at a place in the sky halfway between zenith and horizon, and they will usually point up at about a thirty degree angle!) Eric