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User Name Thread Name Subject Posted
GUEST, topsie Folklore: Rumours you believed as a child (112* d) RE: Folklore: Rumours you believed as a child 13 Nov 15


Nigel Parsons
Date: 12 Nov 15 - 04:50 PM

From: GUEST
Date: 12 Nov 15 - 02:38 PM
"When there's a full moon, low in the sky, it looks very big. However if you bend down and look at it between your legs it's normal size!
This may or may not be true but one thing is certain - you look pretty daft if you test it out!

True!
The moon close to the horizon appears bigger because you are comparing it to whatever else you can see, and because everything else (stars excepted) is closer, your sense of perspective makes the moon seem larger that it is when viewed in the middle of the sky (where it seems small and isolated).
Viewing it through your legs gives you an immediate & reliable sense of proportion, as your legs will be the same size whether you're viewing a moon near the horizon, or in clear space."


THIS IS NOT TRUE

The moon (or sun) appears to be bigger close to the horizon because the image you are seeing is magnified by moisture in the atmosphere through which you see it. Sometimes, if there are strips of cloud in front of it, the magnification varies so that you see a dumb-bell shaped or egg-shaped moon or sun.
We had a discussion about it on mudcat some years ago:

Subject: RE: BS: Spring
From: GUEST, topsie
Date: 25 Feb 11 - 12:20 PM

"I'd never heard of the 'green flash' or 'green rim' before this thread, but the lowest picture in Micca's link [https://en.wikipedia.org/wiki/Green_flash] seems to confirm something I have long suspected - the apparent size of the rising or setting sun or full moon when it is just above the horizon isn't just an illusion caused by its proximity to the trees and rooftops, as many 'experts' claim, but is caused by magnification when it is seen through the atmosphere near the horizon."

From: JohnInKansas
Date: 26 Feb 11 - 07:08 PM

"topsie (12:20 pm):

the apparent size of the rising or setting sun or full moon when it is just above the horizon isn't just an illusion caused by its proximity to the trees and rooftops, as many 'experts' claim, but is caused by magnification when it is seen through the atmosphere near the horizon."

The same magnification is responsible for what's called the "ephemeris jump" (you can look that up) noticed mostly for a setting sun or moon. The sun/moon appears to approach the horizon at "normal rate" until what looks like about the last 5 degrees (where it "should" take about 20 minutes more to reach the horizon) but "plops" out of sight in a minute or less. The effect is especially visible when seen from an airplane at 20 or 30 kft altitude.

John

If John in Kansas agreed with me I MUST be right.)


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