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raaaid
06-06-2007, 07:26 AM
probably sometime you have seen the moon bigger on the horizont, this is something nasa cant explain:

http://science.nasa.gov/headlines/y2005/20jun_moonillusion.htm

a question to pilots here:

have you ever seen the moon to appear bigger on sea horizont?

and about mirages: it would be interesting if we had mirages in bob

you are in the desert and see a city close but you never reach it, cool isnt it?

BSS_Goat
06-06-2007, 07:40 AM
http://forums.ubi.com/images/smilies/blink.gif

DuxCorvan
06-06-2007, 07:57 AM
Well, some scientists say it's due to our animal inheritance: our brain just 'zooms' and 'enhances' any image we see in the horizontal -as reported by our positional equilibrium inner-ear senses- because it was useful for our savannah ancestors, while gives us a 'normal' sight in the vertical.

Birds of prey -eagles and hawks- have much of this perception feature, only in the vertical, because it helps them finding their prey below.

BTW, raaaid, you're much too obsessed with the moon lately... I think I'm going to have a revolver w/ silver bullets at hand.

http://www.hauntedfog.com/images/Foothills/Werewolf_Fangs.jpg

tigertalon
06-06-2007, 08:06 AM
Partially difference in moon (or sun) shape just above horison can be explained by diffraction of light through the atmosphere, where moon/sun is actually a few degrees lower compared to where we see it and is in fact below the horison before we see it go there. Other than that it's an illusion. Simply take an appropriate coin in an extended hand and cover the moon with it when it's high and when it sets/rises. They are equal.

Whirlin_merlin
06-06-2007, 03:15 PM
Originally posted by raaaid:
, this is something nasa cant explain:



'Cameras don't see it, but our eyes do. It's a real illusion.' (From your link).

There is nothing for NASA to explain. It's an illusion, remember you see with your brain not with your eyes.

Daiichidoku
06-06-2007, 03:43 PM
MUAHAHAHA!!!!

i will CRUSH your head!

http://img.photobucket.com/albums/v479/Daiichidoku/CrushYourHead.jpg

http://img.photobucket.com/albums/v479/Daiichidoku/crushhead.png

Capt.LoneRanger
06-06-2007, 03:48 PM
Scientists can very well explain that.

It basically comes down to 2 things:

1. The closer the moon is to the horizon, the more the light gets bent through the atmosphere. It is practically magnified. (as in the link you posted)
2. The main reason why the moon appears to be bigger when closer to the horizon is the fact, that you can compare it to buildings, structures and trees and then you *THINK* it is much larger than when it is high up in the sky. Same is for the sea, as the reflections make it appear much brighter than it really is.

That is also the explanation why cameras usually don't get this effect. You simply see only a short fraction of the horizon or structures and the lighting-difference is much worse, than with the human eye.

Now, that was a simple one.

Divine-Wind
06-06-2007, 03:51 PM
Bloody heck Dux, that picture scared the cr@p out of me. http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif

GreyBeast
06-06-2007, 04:09 PM
The only correct answer so far is Capt.LoneRanger's #2. I´m not too sure about #1, it sounds feasable, but I'm 100% sure it's the fact that your brain compares the moon's size to landmarks and buildings the closer it gets to the horizon. If you were to "measure" its diameter with a ruler along its path across the sky, you'd notice it doesn't change size.

Humans don't have rulers or tape measures or thermometers in them, we can tell near or far, hot or cold and so on by COMPARISON.

Capt.LoneRanger
06-06-2007, 04:13 PM
Well, No.1 is the same phenomenon, that makes the moon appear darker or red sometimes, but of course this magnification is marginal! It's not like the moon is twice as big or something.

LEXX_Luthor
06-06-2007, 04:30 PM
All you need is LOMAC, it has a giant arcade gaming moon. And the LOMAC moon is always full.

Cajun76
06-06-2007, 04:38 PM
luna
lune
lunar
lunatic

Divine-Wind
06-06-2007, 05:03 PM
luneartic

tigertalon
06-06-2007, 05:09 PM
Originally posted by Capt.LoneRanger:
Well, No.1 is the same phenomenon, that makes the moon appear darker or red sometimes, but of course this magnification is marginal! It's not like the moon is twice as big or something.

Well, moon/sun actually shrinks when it is very low over horison due to effect in question here, the effective area (or space angle if you want) that it covers is smaller than when it's high up. Reason for that being that light from its lower border travels larger distance through atmosphere and thus bents more on the way to human eye than the light from upper border, in effect making moon/sun look like an ellipse with its horisontal axis unchanged (same as the diameter of a moon when high), and it's vertical axis shrinked. I joted this down in a few secs, red is what an eye sees, and black is actual moon and it's size when it's high up:

http://img.photobucket.com/albums/v662/aegeeaddict/Moon.jpg

Lurch1962
06-06-2007, 05:57 PM
tigertalon,
Riiight on, man! Some other factors to bear in mind...

The density of the atmosphere varies (to any meaningful degree) only in the vertical, and as such can be considered to be "horizontally layered." Refraction therefore works only in the vertical direction, and in the vast majority of cases causes a vertical "squashing." In normal atmospheric conditions, the refraction of an object on the horizon amounts to 34 arcminutes, or just over half a degree.

However, there are some times (and I've seen 'em in the arctic) when temperature inversions can cause vertical stretching and other distortions.

But the main thing is this--atmospheric refraction will never cause a horizontal stretching.

Another little-known wrinkle on the Moon illusion. When the moon is near the horizon, it's actually FARTHER AWAY from you than when it's high up in the sky. That's because you're seeing the moon from a point halfway around the earth, so-to-speak. As seen from the moon, you would be on the limb, halfway between the nearest and farthest sides of the ball of the planet. This distance difference amounts to the Earth's radius, or about 6,500 km.

--Lurch--

tigertalon
06-06-2007, 06:13 PM
Originally posted by Lurch1962:
tigertalon,
Riiight on, man! Some other factors to bear in mind...

The density of the atmosphere varies (to any meaningful degree) only in the vertical, and as such can be considered to be "horizontally layered." Refraction therefore works only in the vertical direction, and in the vast majority of cases causes a vertical "squashing." In normal atmospheric conditions, the refraction of an object on the horizon amounts to 34 arcminutes, or just over half a degree.


Isn't it a interesting coincidence that this angle equals the angle of the sun/moon disc, =0,51deg?


Originally posted by Lurch1962:
However, there are some times (and I've seen 'em in the arctic) when temperature inversions can cause vertical stretching and other distortions.


Thx, never knew stretching was possible in the atmosphere. Temperature inversion however has to be quite strong to compensate for the difference between the distances that "lower" and "higher" light rays have to travel through atmosphere.


Originally posted by Lurch1962:
Another little-known wrinkle on the Moon illusion. When the moon is near the horizon, it's actually FARTHER AWAY from you than when it's high up in the sky. That's because you're seeing the moon from a point halfway around the earth, so-to-speak. As seen from the moon, you would be on the limb, halfway between the nearest and farthest sides of the ball of the planet. This distance difference amounts to the Earth's radius, or about 6,500 km.

--Lurch--

True, but compared to distance between Earth-Moon (around 400.000 km) still neglectable. The thing is, that we assume objects high on the sky to be closer to us than the ones just above horison, it's our perception based on our experience: usually objects you see at a steep angle above yourself (planes, birds, leaves, clouds etc etc) are indeed closer than the ones you can barely see in the distance, that's why by this "false" assumption moon should get smaller and smaller when falling down to horison, as it is, by our perception, moving "away" from us. Well, actually moon stays exactly same, so our only "logical" explanation is that it must have grown bigger...

raaaid
06-07-2007, 03:55 AM
you are worse than me trying to give an explanation to everything

people has written full books trying to explain this illusion

for me as many things this is a total mistery, im unable to explain it because ive seen the moon in the horizont and it doesnt look like the picture

i mean do you think you could reproduce this illusion with the best virtual reality?

if you are not then you dont understand it

tigertalon
06-07-2007, 05:27 AM
Read the page you posted link to. No need to read a whole book on that and it doesn't take a genious to understand that couple of lines.

Whirlin_merlin
06-07-2007, 07:09 AM
Originally posted by raaaid:
you are worse than me trying to give an explanation to everything

people has written full books trying to explain this illusion

for me as many things this is a total mistery, im unable to explain it because ive seen the moon in the horizont and it doesnt look like the picture

i mean do you think you could reproduce this illusion with the best virtual reality?

if you are not then you dont understand it

Let's try again. The Moon is not enlarged it just seems like it. There is no strange penonenomenomenomenom here, it's just a quirk in the way we see things.

Let's put it this way it would still fill the same ammount of your gunsight.

VF-17_Jolly
06-07-2007, 01:32 PM
http://img.photobucket.com/albums/v435/POLISH_PILOT/joe.jpg

Akronnick
06-07-2007, 01:40 PM
It's all in your brain, the moon is always(aproximately) the same apparent size when viewed from the Earth's surface.

The apparent enlargement of the Moon happens only in your brain.

Remember, the image that falls on your retina is upside down and backwards, but the brain interprets the image to what we see.

The brain, for the most part, sees what it wants to see. That is how all optical illusions work.

The 'Huge Moon' is just that, an optical illusion, nothing more.

HayateAce
06-07-2007, 01:46 PM
moon illushion

http://www.fototime.com/31ACF054C4F7202/standard.jpg

Rattler68
06-07-2007, 01:46 PM
When the moon in low on the horizon, the direct path light takes to get to your eye travels though an apparent thicker section of the atmosphere (it's hitting at an angle: sloped armour works this way too - it's not thicker, just angled to cause a direct path to travel more down the long axis of the material). This causes more diffraction. As it rises, the direct path of light from the moon travels through a more uniform thickness of atmosphere.

The mention earlier about measuring size to references on the horizon itself (buildings, etc.) also contributes, but less so. It appears this way in cities, or on the ocean.