The Moon Illusion

[bascule]

Everyone knows the moon appears larger on the horizon. Before we even discuss this, I don't anyone to dismiss for a second that this is 100% a neurological effect and not some kind of actual optical effect perpetrated by the atmosphere. To dismiss the latter I offer the following:

 

1. Cameras do not observe the moon illusion. The moon appears the same size in photographs on the horizon or in the sky.

 

2. The size of the moon as projected by the lens of our eye onto our retina is constant no matter where in the sky the moon is located (~.55mm I believe, correct me if I'm wrong)

 

Some wish to discuss the "theater" of consciousness (as in a Cartesian theater) but I would rather discuss this in terms of Daniel Dennett's "projector" of the conscious experience (i.e. a meme/phenom pool located in our cerebral cortex into which all of the centers in our mammalian brain constantly inject their data, allowing it to feed back on itself)

 

So what I would like to ask is... is the moon illusion perpetrated by some kind of sensory post-processing which can actually alter the perceived resolution (and therefore potential interpolative) detail? Dennett discussed these kind of effects as either being Stalinesque (i.e. before entering your cerebral cortex ala Stalin's mock trials which are a deception which can be experienced by an observer) or Orwellian (i.e. post-experiential revision ala the Ministry of Information's alteration of the historical record in order to elicit social control).

 

I contend that the Moon Illusion is a Stalinesque deception, and somewhere before the phenoms of our visual processing center enter our cerebral cortex and are thus subjected to abstract processing, the image is scaled by some sort of visual preprocessing center.

 

I base this on my own observations of the moon illusion. I suffer from astigmatism and therefore typically see the moon high in the sky as a large blurry blob (as I rarely wear my glasses, unless I'm driving or at work). But on the horizon, I can make out considerably more detail.

 

Thoughts?

[ecoli]

I didn't even know that happened.

[starbug1]

Oculomotor macropsia

[swansont]

Explaining the Moon Illusion

[YT2095]

Everyone knows the moon appears larger on the horizon. Before we even discuss this' date=' I don't anyone to dismiss for a second that this is 100% a neurological effect and not some kind of actual optical effect perpetrated by the atmosphere. To dismiss the latter I offer the following:

 

1. Cameras do not observe the moon illusion. The moon appears the same size in photographs on the horizon or in the sky.

[/quote']

 

is this true then?

I Never knew that! so then technicaly, if you cover one eye when the moon is looking big, it should appear at normal size again?

that would seem a Logical prediction worth testing,

 

I`ll check this out tonight at about 8:30(ish) it was looking large last night, so it`s an ideal time

[swansont]

is this true then?

I Never knew that! so then technicaly' date=' if you cover one eye when the moon is looking big, it should appear at normal size again?

that would seem a Logical prediction worth testing,

 

I`ll check this out tonight at about 8:30(ish) it was looking large last night, so it`s an ideal time [/quote']

 

No, I don't think it's a steroescopic vision issue. It's a "thinking the moon is physically on the horizon" perception (i.e. thinking it's 20 miles away, instead of >200,000) Photos remove that perception by redefining the context.

 

I've noticed this when a storm passed through a hilly area, so the horizon was only a few miles distant - the rain happening on the horizon isn't due to the clouds (or lack thereof) on the horizon. The clouds you see meeting the horizon are much further away.

[YT2095]

how come a cammera doesn`t pick it up then as stated in point #1.

 

(and ya know, I could swear that I`ve seen it on certain movies where this effect shows too!)

 

so I figured that if it`s a single lens and doesn`t, then logicaly covering One eye should do the same (when the brain adjusts).

 

to be honest with you, all these years I`ve always thought that the atmospheric density (being greater at a side angle) was greater and thus caused a magnifying effect.

 

I hope I haven`t been wrong all these years

I`ve told quite a few people in the past that`s what caused it <insert shamed face> I feel awefull now (

[swansont]

how come a cammera doesn`t pick it up then as stated in point #1.

 

That's a 2-D representation, and so you don't get fooled into thinking about the distance in the same way, AFAIK.

[bascule]

Explaining the Moon Illusion

 

Wow, that was a really awesome article, especially the stereoscopic image they provide as an example of how something our brain misinterprets as being closer to us than it really is as being smaller. View this image as you would a stereogram, as if you were focusing on a distant object:

 

 

Notice that the moon on the right seems both larger and farther away.

 

Their conclusions were:

 

We found that the perceptual system responds as though the horizon moon were at a greater distance than the elevated moon. This is consistent with theories that attribute the illusion to the effects of cues signifying that the horizon moon is much more distant than the elevated moon. Cues to distance are physical properties of stimuli, or physiological states (e.g., convergence) affected by those properties. Different cues lead to different perceptual states. Thus, the term apparent in so-called apparent-distance theories is inappropriate. Rather, we suggest that the physical cues to distance affect both perceived distance and perceived size. The opposing apparent-visual-size theories substitute perceived size for angular size as a cue to distance. Thus, they imply that perceptions cause perceptions.

 

So I would continue to contend that this is a Stalinsque (i.e. pre-experiential) illusion.

 

So the real crazy conclusion we can draw from this is somewhere in the visual centers of our brain is an algorithm for scaling images as we perceive them in the theater of consciousness...

[Bettina]

I'm not convinced yet. I will check what you guys say the next time I see a "large" moon. One more thing......I only see a large moon in the warm, humid, summer months and not in the winter. During the winter months, the moon is always the same size....up or on the horizon.

 

I'm no gonna throw out the magnification yet...

 

Bettina

[bascule]

I'm no gonna throw out the magnification yet...

 

Check swansont's link... it's been scientifically proven that the effect is NOT optical

[Bettina]

Check swansont's link... it's been scientifically proven that the effect is NOT optical

 

I have to test this myself. I'm waiting for a good night.

 

ALso, nobody has answered as to why in the cold winters, the moon "looks" the same size no matter where it is, but not in the summer.

 

Bettina

[bascule]

ALso, nobody has answered as to why in the cold winters, the moon "looks" the same size no matter where it is, but not in the summer.

 

I've never noticed it being seasonal. Here's a guy who observed it happening on the night of the Winter Solstice, and even took pictures to demonstrate that it is an illusion and not an optical effect.

[ronblue]

Physically speaking the optical effect of increased in size when the moon approaches the horizon is very minor compared to the psychological effect. It is not likely the average person could tell that the size increased due to the real optical effect due to changes in wave length of the light.

 

The psychological effect is due to referencing. All information is correlated and cross connected. We have good information about the distance to the horizon, but not the moon. When we compare the visual information we know the moon is further away that we had originally thought so we adjust the size for that distance and thereby increase its size.

 

A F-84 fighter pilot reported that he was being pursued by a long cigar space ship and that it was going to ram him so he was going to bail out. A wise move considering the flight characteristic of a F-84 after a minor collision.

 

Well as it turned out his fountain pen had floated out of his pocket during a dive and he perceived it as a large cigar shaped space ship. He correctly identified the object when the slide project projecting the picture on a screen if it was out of focus.

[Bettina]

I haven't given up yet. All I know is the summer moon is H U G E when its low in the sky, and it never happens in the winter.

 

I keep checking, but its cooler out now and its small all the time. This may take awhile to convince me but I got my camera ready.

 

Bettina

[alt_f13]

I haven't given up yet. All I know is the summer moon is H U G E when its low in the sky' date=' and it never happens in the winter.

 

I keep checking, but its cooler out now and its small all the time. This may take awhile to convince me but I got my camera ready.

 

Bettina[/quote']

 

The question I think you are asking is "Does the density of a light transfering medium change the rate of magnification of the light that passes through it?"

 

If it did, according to your cold air theory, when you went swimming your hands and feet would look tiny, and the rest of the world would be in "fish eye," except there would be no focal point (which is not possible.)

 

I say the temperature of the air has nothing to do with it.

 

 

And ronblue, if the wavelenght of light changed how large an object looked, wouldn't the green and red smileys on SFN look to be completely different sizes?

 

Our picture of the world would be pretty distorted if color = magnification.

[swansont]

It's an illusion, so there's a chance that some people do not see the effect. You may be less "fooled" when the horizon has fewer objects for comparison, like no leaves on the trees, etc.

[Bettina]

The question I think you are asking is "Does the density of a light transfering medium change the rate of magnification of the light that passes through it?"

 

If it did' date=' according to your cold air theory, when you went swimming your hands and feet would look tiny, and the rest of the world would be in "fish eye," except there would be no focal point (which is not possible.)

 

I say the temperature of the air has nothing to do with it.

 

 

And ronblue, if the wavelenght of light changed how large an object looked, wouldn't the green and red smileys on SFN look to be completely different sizes?

 

Our picture of the world would be pretty distorted if color = magnification.[/quote']

 

Its not a cold air/warm air theory. I know I'm being fooled like you guys have said, but I want to know why the moon never looks "big" in the winter no matter where it is positioned.

 

The summer air holds lots of heat and moisture where winter air is dryer and clearer.

 

I got my ruler and camera ready.

 

Bettina

[alt_f13]

The ruler and camera will do no good, aside from proving the moon doesn't actually change size or distance on a perceptual level. I suppose that is what you are trying to convince yourself of, but doesn't the fact that the moon is actually farther away from you when it is on the horizon prove that?

 

Try and position the moon on a treeline horizon about .5km from you or behind a large (tall) city. That always does it for me.

 

You don't happen to have a summer/winter home do you?

[Bettina]

The ruler and camera will do no good' date=' aside from proving the moon doesn't actually change size or distance on a perceptual level. I suppose that is what you are trying to convince yourself of, but doesn't the fact that the moon is actually farther away from you when it is on the horizon prove that?

 

Try and position the moon on a treeline horizon about .5km from you or behind a large (tall) city. That always does it for me.

 

You don't happen to have a summer/winter home do you? [/quote']

 

No, we don't have a summer/winter home so this will take some time. I always thought the moon looked larger at the horizon because I was looking thru smog, pollution, and humidity which caused a magnifying effect.

 

Now that its proven wrong, I want to see for myself......and I will.

 

Bettina

[bascule]

The easiest way to prove it to yourself is look at the moon on the horizon through a paper towel tube. The moon will appear smaller when you look at it through the tube than it does without it.

[Bettina]

The easiest way to prove it to yourself is look at the moon on the horizon through a paper towel tube. The moon will appear smaller when you look at it through the tube than it does without it.

 

I'm ready to do what you asked, but I have yet to see a large moon on the horizon like I do in the summer..

 

But I'm still waiting......and I have the paper tube.

 

Bettina

[Conceptual]

A few summers ago, while staying at the beach in NE, the moon came up from the ocean horizon and appeared blood red, but of the same size. it did this severals days in a row many others saw it. On the last day someone took a picture with a digital camera and moon appeared less than white but not red.

[Bettina]

I found this article. http://facstaff.uww.edu/mccreadd/ It says the moon illusion is a summer event. I saw the moon tonight, but was a little late and it was already at about 20 degrees.

 

However, it looked white, and small, very unlike a summer moon.

I guess I'll have to wait till summer. I really wanted to try the tube thing.

 

I'm a believer, but I just wanted to see for myself.

 

Bettina

[mauy]

this was an amazing thread , i really enjoyed reading this