Talk:Moon illusion

The moon illusion is currently UNEXPLAINED
THESE REMARKS REFER TO AN OLD (2005) VERSION. It has been extensively revised in 2008.

http://www.google.com/search?hl=en&lr=&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=%22moon+illusion%22+%22is+still+unexplained%22&btnG=Search

We need to rewrite the "cause" to reflect the current body of evidence. I don't have time right now, but people shouldn't be misled by an explanation of an unexplained phenomenon. There is no mention of this being a spectulation or otherwise. This is deceptive.
 * Above is by User:Jabin1979. Mgm|(talk) 10:42, Mar 7, 2005 (UTC)

If I can find the time, I'll see if I can do a rewrite on the info to make the status of the info clearer. Mgm|(talk) 10:39, Mar 7, 2005 (UTC)


 * I don't buy the google link at all. The article by Maurice Hershenson is listed in two of the four results. There's a much more scientific, and IMHO, better explanation already listed on this page. If you want to skip the technical aspects, just examine the 'big man/little man' pictures on the last page of the Micropsia site: http://facstaff.uww.edu/mccreadd/appendix2.htm Krupo 14:57, July 24, 2005 (UTC)

Also, change your google search and get 7400 pages that state the opposite: http://www.google.ca/search?num=100&hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=%22moon+illusion%22+%22explained%22&btnG=Search&meta=

After looking through all those pages, I can't seem to find "the" answer. If we are going to say this illusion is "solved" once and for all, we need A) A citation in a peer reviewed journal (not just what one psycholigist says on his webpage (or even worse, The Straight Dope) or B) an established consensus among a large number of experts found on Google. I do think now that it is closer to being solved than not.  Citing any one physicist or psychologist would be bad research however,  we really need something more widely accepted.  If someone writes that it's "solved" on here, it would be best if you provide a number of strong sources annotating each page to show a consensus.

There definitely isn't a consensus. I can cite The Columbus Dispatch, June 22, B7: Richard Pogge and Gerald Newsom, two Astronomy professors at OSU, have two different explainations. James Todd, a psychology professor in the field of visual perception at OSU, says, "We can explain a lot of illusions, but this one is a particularly tough one." They also quote several other people. Before stating this illusion as "explained," I would insure there is an consensus among experts, maybe several emails?

Non-possiblities
Just to clarify, things such as Diffraction of light also don't answer the question. Diffraction only changes it slightly, while what we see is a much bigger difference. Another possiblity proposed is that the Moon in comparison with smaller objects near the horizon makes it seem larger. 128.6.175.26 16:51, 2 February 2006 (UTC)

What a mess this has become
First there is this: "This explanation is, of course, the apparent distance theory which now is rejected by modern vision researchers who have specifically researched the moon illusion. See below." (and yes, I wrote most of the paragraphs that that follows)

I think there are far better ways of doing this. One...I personally don't agree that the "experts" which rejected that hypothesis are any more credible than those who advocate it. Regardless...you should reorganize the page, and put that section into the appropriate subsection, rather than just saying "this is discredited, see below".

Then further on there is "for the latest research do a web search for "moon illusion." " and repeated "for details see link to "the moon illusion explained." " That sort of thing is exceptionally unprofessional looking in an encyclopedia.

I suggest this page be marked as "not conforming to quality standards" or whatever. What process do we need to go through to do that?

--Robbrown 05:47, 15 April 2006 (UTC)

Field of view theory
I'm surprised this theory isn't mentioned. Everybody who has delved into photography knows about it.

The synopsis and premise is quite simple: When you look at an object on a uniform surface with little background clutter, your eyes make larger motions since your brain is able to process the little amount of information per degree. When you place the same object in a cluttered background (near the horizon you usually have multiple trees, houses, lights, as well as a lot of motion), your eyes don't make that much motion since the brain must process a lot more information per degree, thus your field of view narrows and you focus on objects in the center of the image.

This presents an ability to train the brain in overcoming the illusion. Once you stare long enough on the Moon, it should seem to have grown larger (if only for a short moment). Key to successfully doing this lies in being completely relaxed. If you get even a bit startled, you'll almost immediately lose the narrower field of view.

Comparison Photo
an example of comparison photos would really be good. ive been waiting for a 'big' moon for a while to snap a shot of it, but it hasnt happened yet.

although it may be that while the photos did show them to be the same size, that it would seem irrelevant since you can't see it 'big' to compare. Sahuagin 18:26, 29 October 2006 (UTC)

Discovering the Illusion
I'm surprised that what (for me!) is the most compelling demonstration that this is an illusion is not mentioned. Namely, look at the Moon when it is near the horizon through a tube (like a toilet paper tube, or the tube used as a core for paper towels--or even through the space made by your hands and thumb) and suddenly it looks small again!

Also, concerning the explanation: "The problem is, of course, that our neural nets are not trained to see objects more than some 100 meters away." There is perhaps a citation for this "fact"? First, it seems to presuppose that the brain is organized in the form of neural nets; I'm not sure that is accepted (although maybe it is, and I'm just ignorant of it). Second, it seems to imply that someone's neural nets could be trained to "see" objects further away, and if this were done, the illusion would vanish, or at least diminish. (Or more easily tested, if someone had spent their life seeing only nearby things, and were then given glasses allowing them to see things further away, the illusion would be even more compelling than it is for those of us who have had good vision all our lives.) But third, it is not at all apparent what it means to _not_ be able "to see" objects more than some 100 meters away."  Obviously we do see objects further away, the Moon being one of them.  So what does "see" mean in this context?

Finally, since this is an illusion, I presume that you can't discern any smaller areas on the Moon when it is near the horizon than when it is high--that is, it would be no easier to see the large craters, or "bays" in the maria. I have tried unsuccessfully to tell whether this is true, nor have I ever seen any discussion. It would be illuminating (pardon the pun). —Preceding unsigned comment added by Mcswell (talk • contribs) 01:23, 12 May 2008 (UTC)

Illusion?
I've never noticed the difference between rising and zenith moons before, but I have noticed the varying sizes of the moon many times. (Never thought about how high in the sky the moon was at the times, strangely enough..) And, well, I'm not sure if this is the same thing then, but the differences in size that I have noticed are definitively *not* an illusion, sometimes the difference can be as much as ten times! On some nights, the moon can be so small as to be nearly a tiny dot, but on others it can be larger than a plate. And when it's small, I can't discern any of the craters, but when it's large, they are all very visible. Also, allthough I haven't made a point of noticing the height of the moon, I have noticed that on the few times the moon has been particullary large, it has been consistently large all through the night, likewise when it comes to the small moons. On this page "http://www.mhmyers.com/moon.tn.html#moonillusion" it mentions that "If you place your thumb and index finger a pencil width apart and hold it at arm's length, you will always be able to fit the moon between them no matter where it is." which is simply not true. Sometimes the moon has been as large as my hand when I've tried this. This page, while trying to explain the "illusion" even illustrates it very good with two photos: http://niquette.com/books/sophmag/moonill.htm While, yes, they are the same size on the photos, the topmost photo is the result of a zoom, unless the moon was large to begin with. And the one with the mountains? I rarely see such a large moon, even when it is on the horizon, so.... My question then is, is there a real effect of moon sizes not mentioned in this article, or is what I'm talking about the same thing as the "moon illusion"?

- NightRaven


 * Just an update, I just came in, and the current moon is thrice as large as usual, and it is in the middle of the sky, nowhere near the horizon. Is this page a hoax?

-NightRaven —Preceding unsigned comment added by 90.149.29.3 (talk) 17:34, 17 February 2008 (UTC)


 * I think your post is a hoax. You cannot be serious!76.113.105.186 (talk) 05:38, 23 October 2010 (UTC)

If you are not being deliberately vexatious with your claims, then you have a vision problem. You cannot possibly have been able to hold your hand at arm's length in front of the moon and still be able to see any of the moon beyond the edges of your hand unless the moon was well off centre of your hand. Against my better judgement, I will take your claim that "the moon is thrice as large as normal" to be an effect that you truly perceive (rather than you just getting a kick out of stating nonsense just to hear others get worked up about it). Go and see a neurologist; you have a problem with your visual processing. I am serious. Please hand your license in if you drive; you cannot do so safely. ALso, do you realise the statement "the differences in size that I have noticed are definitively *not* an illusion", cannot be proved? None of us can prove that anything we see is real. We can, however, ask if others see it. If everyone sees it but simple measurement can prove the thing is not real, then it is an illusion, common to most because we process visual signals similarly. If no one else, or almost no one else sees it, then you are right, it is not an illusion... it is a hallucination; a visual signal creating a perception of something that is not real and is generated entirely within the brain. There is no way to photograph the effect; photos where the moon appears large in comparison to, say, a person near it, are zoomed. You cannot perceive "zoom" in a photo; I can make the moon look three times larger by moving three times the distance from the person, zooming in by a factor of three, and taking the photo. The person will appear the same size as in the unzoomed photo but the moon will be three times larger, becasue I am not changing my distance from it. The moon's change in size due to orbital distance changes are far smaller than you claim; about ten percent. I think you are thinking of the different sizes of the moon in photos that are zoomed to varying degrees. (203.84.132.206 (talk) 00:45, 28 November 2012 (UTC))

Excuse me for pointing out that excessive effort is being expended on the illusion as a physical or physiological phenomenon rather than explaining why the eye-brain system evolved this feature to assure the successful perpetuation of genes. Full disclosure: I am the author of The Moon Illusion at http://niquette.com/books/sophmag/moonill.htm, which addresses this issue, and I am disappointed that no External Link has been included in this article, which might well inspire further references and investigations by evolutionary experts. Paul Niquette (talk) 12:05, 23 May 2013 (UTC)

This article confuses me
Just thought I'd mention that. It seems to be written like a (bad) academic paper, not an encyclopedia article. What is the illusion? Why does it happen? Did this have an impact on any events in the real world at any time? Mythologies, theories? Why is there enough geometry to make my eyes bleed? --99.236.163.79 (talk) 04:52, 16 March 2008 (UTC)

I agree, this is a very confusing article. It's very much below par compared to most other wikipedia articles. I (tried to) read this article and now know less about the moon illusion than I did before I read it! And I'm an astronomer! -- JSF, --35.8.153.13 (talk) 19:36, 18 April 2008 (UTC)

What on earth has happened to this article?
When I last looked here 18 months ago, this article was much better. It described the illusion and gave a few brief plausible explanations. Now the article is 5 times longer, is full of strange notation and strange explanations, and is far less encyclopedic. Is this a subtle form of vandalism? Occultations (talk) 15:22, 21 March 2008 (UTC)

I totally aggree. It looks more like a conference paper than an encyclopedic entry. I think the article should be restored to what it was then. Tó campos (talk) 18:16, 24 March 2008 (UTC)

Avargasm (talk) 21:51, 5 May 2008 (UTC) I agree with you both. Seems like someone has done a big self research. I am returning the article to the point where it was concise and had meaning and usefulness.

We must remember that web pages are generally not an acceptable source of citations for Wikipedia articles. Contributors: please take this into account: (from: What Wikipedia is not)

please do not use Wikipedia for any of the following:

1. Primary (original) research such as proposing theories and solutions, original ideas, defining terms, coining new words, etcetera. If you have done primary research on a topic, publish your results in other venues such as peer-reviewed journals, other printed forms, or respected online sites, and Wikipedia will report about your work once it becomes part of accepted knowledge.

It's a plausible theory, but when you look at the evidence, the atmosphere is clearly acting as a lens and bending the light. See the photos of the moon through the atmosphere from the space station for proof that the 'Illusion Theories' are completely wrong, although, it was a reasonable explanation before we knew the facts. concerned scientist —Preceding unsigned comment added by 75.162.34.110 (talk) 12:26, 14 May 2010 (UTC)

The atmosphere can only act as a lens in a horizontal direction, because its density changes with height, but the density is the same along any horizontal plane; the moon looks round regardless of its height, whereas the effect you speak of would be like a fun house mirror, magnified in only one direction. Put yourself on the side of a steep hill when the moon is high in the sky, so that, because of the hill, the moon is near the ground. You will see that it appears to increase in size — Preceding unsigned comment added by 203.84.132.206 (talk) 00:51, 28 November 2012 (UTC)

Reply to "What has happened?"
NOTE added May 14, 2008. A revision of the long article you refer to was in progress on May 12, to make it more user friendly. But this revising stopped because someone removed that "long" article and substituted for it an entry that was unsatisfactory. However, a different user,(see the next entry in talk by 81.157.197.236) now is providing a well-written summary. Here is a word of friendly advice to others who plan to comment on the moon illusion: First read, for instance, the excellent book, "The Mystery of the Moon Illusion" by Ross and Plug (2002). It will bring you up to date with modern visual science. Since 1985 there has been a radical change in how vision scientists describe and explain classic visual illusions, including the moon illusion. The terms, equations and diagrams of this new approach (paradigm) have appeared only in refereed journals, in two "moon illusion" books (1989, 2002) and in only two or three websites (including "The Moon Illusion Explained.") This new approach emphasizes that the moon illusion for most people begins as an angular size illusion. This definition is accepted and emphasized in the Ross & Plug (2002) book, etc..

The (now removed) article you referred to was too long because it used seemingly "strange" terms, concepts, equations, and diagrams not yet offered elsewhere in Wikipedia. (Such as, perceived visual angle, perceived linear size, size-distance invariance, perceptual size-distance invariance, angular size contrast, linear size constancy, equidistance tendency, and oculomotor micropsia.)

Likewise, the Wikipedia entries for other classic "size" illusions (such as the Ponzo illusion and Convergence micropsia ) have not yet been revised to also describe them in terms of the new paradigm, and thereby relate them to the moon illusion. It has been a giant step forward to show that the basic moon illusion (the visual angle illusion) is an example of the well-known relative angular size contrast illusions or else the illusons of oculomotor micropsia. But that merely redescribes it. The main task facing researchers is to explain why those two more basic illusions occur. Various theories currently are being considered. They are complicated and differ widely in the kind of brain activities they propose. These theories are not yet reviewed in Wikipedia.

The moon illusion will not be fully "explained" until an agreement is reached on those more basic theories. tit ding unsigned comment added by Mccreadd (talk • contribs) 22:08, 22 March 2008 (UTC)

Pruning too extreme
Fair enough, this article had become overblown and dauntingly complicated, but now it has been decimated to such an extent that lots of valuable information from earlier versions has been lost, and what's left has in some places become so sketchy as to be pretty much useless. As I get around to it, I will be re-adding some text from an earlier version. 81.157.197.236 (talk) 11:07, 13 May 2008 (UTC).

Avargasm (talk) 06:26, 26 May 2008 (UTC) Sorry if the pruning was too extreme, and thank you for re-adding the lost info. The article seems much better now IMHO, without the overwhelming details of this or that theory. I recommend to keep this style, and if a deep technical discussion is needed, I suggest to do it in a separate article for that theory alone.

Is relative size hypothesis a particular case of the apparent distance hipotesis?
The apparent distance hypothesis is the general explanation about "cues" that make us think that objects near the horizon are further away than others. In this scenario, it seems to me that the relative size hypothesis is only a special case of "cues", that is, small objects in moon's immediate visual environment give us a "cue" that the moon is at great distance. This "relative size cues" are even mentioned in the apparent distance hypothesis. Avargasm (talk) 06:39, 26 May 2008 (UTC)

No, it is a serious mistake to think the two theories are the same.
The obvious connection between distance cues and "relative sizes" has been exploited by all "relative size" moon illusion researchers at least since Restle's (1970) article in Science, which made it perfectly clear that the crucial variable is the relative perceived angular size, not the relative perceived linear size.

At least since 1962 the relative perceived angular size theory has been the best known alternative to the apparent distance theory which, as all researchers know,  can explain a relative linear size illusion, but cannot logically explain the relative angular size illusion that most people have for the moon.

I echo the earlier request (May 14, by user Mccreadd) that contributors to this "TALK" section get familiar with the extensive published research on the moon illusion before they offer suggestions like that. The book by Ross and Plug (2002) reviews research up to 2001. Reviews of research since 2001 can be found in "The Moon Illusion Explained" (the only website Ross and Plug referred to.)  (That website's Section II reviews the relative size theory and specifically mentions "The Distance-Cue Connection.") Ojosepa (talk) 16:59, 7 June 2008 (UTC)

Expand the illusion
IMHO the sun can not randomly have offsetting distance and size differences from the moon, perfectly perhaps there is a larger illusion containing this one

Past cultures on earth have cosmologies that have this at their centers why does ours completely ignore it????? 32.139.49.166 (talk) 11:24, 7 June 2008 (UTC)

"Point of reference" theory
Someone has plonked the following text in an inappropriate place in the article:


 * "Another theory is called point of reference. When the moon is near the horizon there are usually common objects in the foreground (trees, telephone poles etc.) that give a point of reference. Therefore the moon appears bigger next to an object for which the observer has a reference of size. As the moon travels higher in the sky the observer loses this point of reference for comparison therefore the moon appears to be smaller than when it is close to the horizon."

If this is a separate theory then it need to go in a separate section. Or is it basically the same as the "Relative size hypothesis", and should therefore be merged into that section? If it's not the same then I think the difference between the two ideally needs to be explained better. I'll leave this to someone more knowledgeable than me to sort out! —Preceding unsigned comment added by 86.134.55.109 (talk) 03:20, 6 October 2008 (UTC)

Is the moon the real issue here?
Forgive my naivete or inopportuneness, but I thought I could express a couple of thoughts here.

The perception of the sun behaves in the same way. Last week I was driving on a highway around sunset and I saw a sun that was huge, not just 20% or 100% bigger, but probably 10 times bigger than usual. So the effect in question is really remarkable.

I believe that what gets enlarged in our visual perception is not the moon (or the sun) itself, but any object that happens to occupy that same spot of our visual field that the moon is occupying. It could be a group of trees that overlap with the moon. As a simple example, suppose that at a particular moment the moon is exactly enclosed between two distant tall trees, one to the left and one to the right of the moon, and looks huge. I believe that we would perceive the distance between those two trees as being the same (and seriously enlarged!) even if the moon were not there. This means that we are not magnifying *the moon* in our perception, we are magnifying just everything that is contained within a certain portion of our visual field (a wide and long vertical strip of space running parallel to the horizon).

In other words, sometimes our whole perception of space is distorted, making far objects appear to us angularly larger than they are. Now, we must also infer that when there is continuity of perspective cues from where we are to where those trees are, *the whole space* between us and the horizon (not only the space near the horizon) is also (continuously) distorted in our perception. In other words, our perception of space based on perspective cues can produce suprisingly wrong results at times. Sometimes the perceived angular size of distant objects will be wrong (perhaps with a smaller error for closer objects and larger error for farther objects). I suppose our perception system first builds a model of space (and things contained therein) from all the available perspective cues (some of which may be ambiguous), and then possibly "adjusts" the perceived angular size of the objects that lie in certain parts of the space to make them fit in that model. Again, it's not just the angular size of the *moon* that gets adjusted, it's the angular sizes of *everything* that lies within a certain vertical strip of space running parallel to the horizon, and probably also of everything else that we are seeing, to an extent varying with the real distance of each object. I suppose the cause lies in a misinterpretation of ambiguous perspective cues by the visual system, which ends up underestimating or overestimating the distance of some objects. The error and the adjustment will depend on the actual distance of each object as well as on the misleading perspective cues. When the moon or sun is up in the sky, there will be no chance of the visual system being misled by ambiguous perspective cues.

The interesting conclusion is that the poor moon has nothing to do with this effect, which exists independent of its presence or position in the sky. Rather, the moon acts as a sort of reference measure, providing us with a way to perceive (perhaps even measure) the effect of the distortion in our perceived space due to the automatic resolution of ambiguous perspective clues by our visual system.

Moreover, the effect probably happens much more often than we believe, but we only notice it when the moon or the sun happens to be within the "stretched" portion of the visual space. If there are only trees and buildings in there, we probably won't notice anything strange.

—Preceding unsigned comment added by 216.86.58.66 (talk) 20:24, 25 February 2009 (UTC)

Alessandro —Preceding unsigned comment added by 216.86.58.66 (talk) 20:08, 25 February 2009 (UTC)

Angle of regard hypothesis
The Angle of regard hypothesis is easily disproved with computer graphics. Since the section has no references - I've removed it. SteveBaker (talk) 23:20, 26 November 2009 (UTC)

Bizarre Rationalization
The moon not only looks bigger at the horizon, it also looks squashed! And it always looks squashed whether you are seeing it in the desert with nothing around, or in the city with buildings. That means only one thing: Lens Effect from the atmosphere. To see more proof of the lens effect of our atmosphere, check out image #7 at: http://www.boston.com/bigpicture/2009/06/recent_scenes_from_the_iss.html That is not an illusion, the lens effect is bending light. Now that's science! —Preceding unsigned comment added by 75.162.34.110 (talk) 12:19, 14 May 2010 (UTC)

Here's another image of the moon: http://twitpic.com/1bz3nm Clearly this is the lens effect, it has nothing to do with 'illusions'. —Preceding unsigned comment added by 75.162.50.219 (talk) 21:00, 15 May 2010 (UTC)


 * If you are in the vacuum of space and you look through the entire atmosphere at such an incredibly shallow angle, I grant that you will get some atmospheric distortion. However, down here on the surface of the earth, that effect is utterly negligable.  But I beg that you don't take my word for it.  The illusion is trivially demonstrated - take a UK penny or a US cent or other small coin - and hold it up at arm's length next to the moon at zenith.  Then do the same experiment when the moon is on the horizon.  You will then be completely and 100% convinced that atmospheric lensing has little part in the illusion.  I've done this experiment with my kid and with other doubters a dozen or more times - it is completely and 100% conclusive.  Another way I've demonstrated this is with computer graphics (something I do for a living).  If you draw any small disk on a plain blue or black background - then draw the same disk behind a reasonably realistic scene of the horizon, the disk that's behind the ground clutter looks much larger than the one drawn on a plain background.  And in that case, you can actually do a screen capture of the two images and overlay them one on top of the other to be 100% convinced that the effect is just an illusion.


 * So you are completely and utterly WRONG...and the simplest possible experiments demonstrate that.


 * SteveBaker (talk) 04:02, 17 May 2010 (UTC)

Oculomotor micropsia/macropsia theory
I removed this section - it has no references and definitely cannot be true because the effect is easily reproduced on a computer graphics system when the distance (and therefore focussing effect) is the same for all objects. But in any case, the eye focuses pretty much identically for all distances beyond about 20 meters...so this couldn't be true. SteveBaker (talk) 05:08, 5 June 2010 (UTC)
 * This is actually discussed in one of the external links . I've only skimmed thorough, but it sounds like it's more complicated then our article had explained, but the theory hasn't been dismissed. Notably there appear to be some stimulated images and it seems to me from my brief skim that the theory doesn't actually collapse because the effect can be reproduced in a computer graphics sytem. Of course it's possible multiple phenomena may account for the illusion. (I'm not sure how easy it is to prove/disprove that the stimulate illusion is completely the same as the real world phenomena.) Nil Einne (talk) 06:59, 26 September 2010 (UTC)


 * Let me explain in a little more detail.


 * This hypothesis says that when the eye focusses to a different distance than the object is truly at, our estimation of the angle that it subtends changes. This Oculomotor Micropsia theory is absolutely true - and well understood.  What's wrong is the assumption that it can be applied to the Moon Illusion.


 * The implication being made is that if you're focussing on objects that are just a few miles away at the horizon, your perception of the moon (which is a quarter million miles away) would be incorrect - but when the moon is high above the horizon, you are focussing at the true distance of the moon and the error goes away. This seems entirely plausible at first sight - which is why the guy who wrote the web page you linked to has been taken in by it.  But the last step in the chain of reasoning is incorrect:


 * The fact that we see the illusion on computer screens blows it away because in that case we're focussing at a constant distance between eye and screen - no matter whether the simulated moon is on the simulated horizon or not. If this explanation were true - then the illusion would certainly not occur on a computer screen - yet it most definitely does.
 * The theory works because the lens in your eye changes shape when focussing at different distances (which it does - to a point). But that change in shape only happens when focussing down below about 20 meters.  Beyond 20 meters...and certainly out at the horizon, your lens is already stretched out as far as the muscles can possibly stretch it.  Hence there is no change in the shape of the lens when focussing at five miles or at a quarter million miles -the horizon versus the distant moon.  This again, completely busts this argument.


 * It is totally, utterly, impossible for this theory to explain the illusion. SteveBaker (talk) 20:11, 26 September 2010 (UTC)

Ptolemy ?
The section headlined "Possible explanations" refers to a rejection of Ptolemy's theory. But there is no real explanation of what this theory was (just says "refraction theory"). Aristotle was mentioned in the previous section -- did someone confuse the two ? Or were Ptolemy and his theory accidentally deleted ?76.113.105.186 (talk) 05:35, 23 October 2010 (UTC)

Strange Illusion - Related?
I was watching the last full moon, and observed a strange illusion. I was looking at from a grove of trees as it rose above the horizon. After a minute or so, I noticed that in my vision, the moon started to rock back and forth. The movement became rapid, and it seemed as if an area around the moon were magnified. It seemed almost like it was flashing back and forth from one space to another. Hard to explain, but it was a very strange illusion that apparently the observer next to me could not see. Was this an optical illusion resulting from a problem with my eyesight? Very confusing. --IronMaidenRocks (talk) 16:08, 10 December 2010 (UTC)


 * I don't think it's a related phenomenon. But if someone standing right next to you didn't see it then it's got to be an illusion of some kind that depends on brain state or something unique to that individual.   Were there any lights nearby?  Streetlights maybe?  Were there other objects in your field of view that were moving?  Perhaps the 60Hz flickering of streetlights could cause some kind of entrainment effect?  It's hard to understand what you might have seen from a description - and it's evidently not easy to explain.  However, I doubt very much that it relates to the moon illusion per-se. SteveBaker (talk) 18:29, 10 December 2010 (UTC)

Where are the time-lapse photographs of moon illusion?
This article just might be like Miracle of the Sun hoax. 30000 to 100,000 people claim miracle but only 7-8 repeated witnesses found on net. Likewise this article and other moon illusion supporters claim that moon illusion is verified by photography but no photographs are found on net. Photographs are easiest way to illustrate moon illusion.

What I mean that bigger size of moon is due to Refraction. No psychological angle involved in this phenomenon. This article should be categorized as hoax. रामा (talk) 16:52, 22 March 2011 (UTC)


 * You're completely wrong. Photographs can't reproduce the problem well - it depends on having a wide field of view - and the photo compresses perhaps a 60 degree field of view (as seen by the camera) to maybe 10 degrees as you look at the photo - and that destroys the illusion.  Computer graphics displayed on large format screens (I'm talking about a screen at least three meters across) can easily reproduce the moon illusion using entirely synthetic images - thereby proving that refraction has nothing to do with it.


 * But you don't need any of this fancy tech. One more time folks:  YOU CAN DO A REALLY EASY EXPERIMENT.  Get a small coin - (a US cent or a UK penny works well) - wait for a full moon.  Hold the coin at arms' length over the top of the moon...it'll be roughly the same size...depending on how long your arms are.  This gives you a good idea of how big the moon seems to be.  Wait a few hours and repeat the experiment so you do it once with the moon close to the horizon and again with it high up in the sky.  Note that the size of the moon relative to the coin DOES NOT CHANGE.  That proves, conclusively, that refraction cannot possibly be the cause - if it were, then the size of the moon would appear to change compared to the size of the coin.  The effect can only be happening inside your own head...and that's why it's an optical illusion - albeit a powerful one - just as our article says.


 * Until you do this experiment for yourself - don't even think about claiming that refraction is the cause.


 * SteveBaker (talk) 17:10, 22 March 2011 (UTC)
 * When people in London see 'big moon' at moonrise, I see 'small moon' overhead in India. Stars near circumference of moon are visible to people/astronomers in India but not to people/astronomers in London due to 'big circumference'. This is proof that moon illusion is refraction. रामा (talk) 19:42, 22 March 2011 (UTC)
 * No, that's not "proof". You are just guessing.  Just do the experiment with the coin and you'll be completely convinced. SteveBaker (talk) 20:12, 22 March 2011 (UTC)
 * Guessing? You mean stars near circumference of illusion big moon are not hidden? This moon illusion is elaborate hoax. People claim photograh evidence which does not exist. Personal experiment is original research for wikipedia. As no evidence on net exist, I am going to add hoax category. रामा (talk) 21:17, 22 March 2011 (UTC)


 * Oh jeez...please - just do the experiment. I'm not suggesting that you do the experiment and write about it in the encyclopedia (that would be WP:OR).  I'm suggesting that you do the experiment to convince yourself that what the article says is indeed true.  When you are aware of the truth, you can do  better job of understanding why the article is correct.   Meanwhile, I have removed your category addition.  An optical illusion is not a kind of hoax.  But as you say - it doesn't matter what either you or I think - what matters is what you have reliable sources to show.  So - before you start labeling this phenomena a "hoax", you first have to find a reliable source (within Wikipedia's rather formal meaning of that term) to show that it is a hoax.  Your claims about stars being visible or not is also completely, 100% irrelevant - because it too is WP:OR.  This means you need to find a reference in a book or a science journal that says more or less exactly "The Moon Illusion is a hoax".  Until you find such evidence, you may not add that claim into this article.  Your personal findings are Original research - which counts for absolutely nothing whatever around here.  We have solid references in the article to the fact that this phenomenon is an optical illusion - so until/unless you can find better, more solid references to show that your view is correct - you should not persist in trying to claim that this rather simple illusion is a hoax.  SteveBaker (talk) 22:59, 22 March 2011 (UTC)

Focal Point of Gravitational Bending of Light
I realise that there is controversy, and that this article should seek to present some likely explanations. However, a gravitational lensing effect due to the earth's gravity field would produce a distortion orders of magnitude below what is required to explain the moon illusion. I'd like to exclude this section as pseudoscientific. Especially since it's unreferenced. Larryisgood (talk) 12:49, 25 March 2011 (UTC)


 * Yes - I agree. It's not just "controversial" - it's utterly freaking bat-shit crazy!
 * How big is the gravitational lensing due to a mere planet? The sun bends light from distant stars by 0.00024 of a degree (this was the amount predicted by Einstein in his 1911 paper) - the earth has 330,000 times less gravity!  So what teeny-tiny fraction of a degree would that be?  Certainly not even enough to measure...let alone make a difference to the apparent size of the moon.  This alone completely busts this theory.
 * The top, bottom, left and right of the image of the moon would be "lensed" by very nearly the same angle - so even if lensing DID have a measurable effect, it would alter the position of the moon - but make almost no difference to it's apparent size.
 * This theory is SO far beyond the realms of possibility...it's just laughable! No serious scientist would have come up with it - so we know that the person who posted it either thought it up themselves - or got it from some nut-job pseudo-science source.  But in any case:
 * We don't add stuff to Wikipedia that we just thought up all by ourselves - that's called Original Research and it's strictly disallowed in article content.
 * We require reliable sources for any material that might possible be considered controversial (which this most certainly is!).
 * Hence I reverted that edit on sight. When you see things like this that you're pretty sure is wrong - you don't need to wait and ask - you should Be Bold and just revert it yourself.  So long as you have good reason, you'll get good backup from all of the serious editors around here. SteveBaker (talk) 13:02, 25 March 2011 (UTC)

Disingenuous edit summary
(The following was added to my talk page by Al-Andalusi after my recent edit - moving it here. Response below.) Arc de Ciel (talk) 03:22, 13 June 2012 (UTC)

I came across your edit here which you described as "trying to improve and clarify". However, what I saw was the removal of cited content clearly done with the intention of emphasizing a Euro-centric bias:


 * The reference clearly states that Alhazen "redefined the problem" and that it was a "fundamental reinterpretation". You wrote that Alhazen was "supporting an explanation". In other words, those Brown people are not capable of formulating their own ideas, they can only "support" existing ideas formulated by (superior) Greeks or Europeans.
 * The reference states that Roger Bacon, John Pecham and Witelo, all three, "rephrased Ibn al-Haytham's intervening objects theory of the moon illusion". You removed the bit that says their works were "based on Ibn al-Haytham's explanation" and replaced that with "Through additional works by Roger Bacon, John Pecham and Witelo". Alhazen has become irrelevant it appears.
 * You removed "gradually" from:
 * "The Moon illusion gradually came to be accepted as a psychological phenomenon"
 * when the reference states:
 * "Through these three authors the moon illusion gradually came to be accepted as a psychological phenomenon in Europe". (p. 10)
 * Why ? does it hurt you to know that it took the medieval Europeans a while to digest the discoveries of other people ?

You are clearly dishonest in this regard and I hope that we don't see more of that in the articles on science in medieval Islam. Al-Andalusi (talk) 00:24, 13 June 2012 (UTC)


 * I will thank you not to make assumptions about my motivations.


 * I happened to find this article and noticed that the section was not very well written ‒ and as none of my changes seemed controversial, I didn’t think I needed to leave more than a generic edit summary. I have not read the source you're referring to as I couldn’t find it online, but I didn’t think that my edits were changing anything significant.


 * With regard to your three specific points:


 * 1. Whether or not they are in the source, “redefined the problem” and “fundamental reinterpretation” are subjective, non-rigorous statements. (For example, what is a “fundamental reinterpretation,” and how does it differ from a “regular” reinterpretation? And what specifically was being reinterpreted, and in what way? In fact, “fundamentally” is listed under Manual_of_Style/Words_to_watch, and I think that policy is relevant here.)


 * Also, I think my edit was quite clear that the idea was Alhazen’s, and that he supported it with his own argument. I don’t see why “supported” is a bad word in this context.


 * 2. I don’t think that my edit implied Alhazen to be “irrelevant” at all. To be honest, I think the current text implies Bacon et al to be irrelevant (mere “rephrasings” of someone else’s work ‒ but I’m not really interested in the minutiae of priority/contribution arguments, as the important thing is that we have the knowledge today).


 * Anyways ‒ Alhazen’s argument was clearly not complete, or his conclusion should have been accepted long before the 17th century - especially if Bacon et al backed him up, which I think implies racism to be an unlikely explanation. I assumed that the original author of this line must have meant Bacon et al had made some contributions ‒ otherwise they shouldn’t be mentioned. I have nothing against saying that they were influenced by Alhazen (they were AFAIK), so I reworded the sentence accordingly. The phrase “based on” sounded dubious to me for the same reasons as discussed in the first point, although not as serious, so I assumed that someone would add it back if it was justified.


 * How about “Through his work as well as that of Bacon [et al] and others, ...”? ‒ or, if they truly didn’t contribute much, I would just omit them and say “His conclusion eventually became accepted...”.


 * 3. “Gradually” is also nonspecific etc. I don’t think there is any significant difference in informational content between “it became accepted in the 17th century” and “it gradually became accepted in the 17th century.” If the original writer meant "[the idea] gradually became more accepted, reaching complete acceptance in the 17th century," that wasn't my first interpretation of what it said.


 * Do you object to my other changes? (since you have reverted all of them)
 * -I think that most of the first sentence in the section is not relevant to the article.
 * -I managed to state his argument using one sentence rather than three (without, in my opinion, removing any relevant content)
 * -The “For over 100 years...invariably” statement is also nonspecific and (in my opinion) unencyclopedic; I reworded it and added a CN tag.
 * -“Ptolemy’s theory” is mentioned as “being rejected,” but if he was the first one to propose an explanation then he should be the first one to be mentioned (placing them in temporal order). I did this, although since this is disputed I also pointed that out. I have no problem with changing the wording to, e.g., “It is suggested that Ptolemy attempted to explain...” but I thought that was less clear. I wouldn't mind omitting Ptolemy entirely and just saying, "The earliest attempts to explain the moon illusion involved atmospheric refraction" and going on to describe how Alhazen argued against that.


 * All that being said, I will repeat that I’m not invested in anything, and to be honest, I'm also not all that interested in entering a debate on the history section of a minor science article. Arc de Ciel (talk) 05:05, 13 June 2012 (UTC)


 * Update: Since there's been no response, I reinstated the changes. To address Al-Andalusi's concerns, this time I kept the phrase "based on Ibn al-Haytham's explanation" and replaced "supporting" with "proposing." Arc de Ciel (talk) 20:35, 16 June 2012 (UTC)

You are doing a fine job but here is a source you can use to sort out Ptolemy (and al-Haytham) in the Almagest Ptolemy advocates atmospheric refraction as the cause. In Optics Ptolemy repudiates refraction and advocates the size/distance hypothesis. Later authors ignored Ptolemy"s psychological explanation until al-Haytam, profoundly influenced by Ptolemy, advocated for a psychological cause in his own Book of Optics   I hope this helps remember assume good faith and be boldJ8079s (talk) 04:44, 15 July 2012 (UTC)


 * Thanks for your confidence. :-) I wasn't sure of Ptolemy, mainly based on reference 5: the source is here, and analyses the text of both the Almagest and Optics. I'm not sure if this may be a fringe position, but no immediate red flags jump out at me from a reading of the text.


 * At the same time, having read that source again I notice that it only argues that Ptolemy didn't propose the size/distance hypothesis, so I've updated the article to correspond to that. I didn't say anything about any influence on al-Haytham (I'm not sure how that should be handled if there are other sources saying al-Haytham's explanation was independent); I also didn't change the "based on al-Haytham's explanation" statement since Al-Andalusi says it is the wording from the source (Henderson), although I can't access it myself. Arc de Ciel (talk) 21:59, 15 July 2012 (UTC)

Watching the moon upside-down
I’m afraid I don’t have any reference and cannot cite any sources, but … somewhere I read that the illusion disappears as soon as you watch the moon upside-down, e. g. by standing backwards, bending down, and looking through your legs. As far as I’m concerned this works, but I cannot tell whether others have the same perception. Does anybody have more reliable information about this? --78.48.76.73 (talk) 21:36, 9 April 2013 (UTC)
 * It’s me again, and in the meantime I’ve stumbled across those two articles: Perceived size and perceived distance of targets viewed from between the legs: Evidence for proprioceptive theory (Atsuki Higashiyama and Kohei Adachi, 2006) and The moon illusion: a different view through the legs (Stanley Coren, 1992). --78.49.202.133 (talk) 23:37, 14 November 2013 (UTC)

Schopenhauer's explanation warrants it's own sub-section?
Doesn't Schopenhauer's explanation about how we perceive things at the horizon to be farther away than things directly above us (and thus physically larger when they are optically the same size), warrant it's own sub-paragraph, along side the other three existing subparagraphs? Right now it's tucked away in the introduction piece of the "Possible explanations" paragraph but it's an explanation that is well sourced within this article (with 2 source links) and an explanation that you still hear being used very often. I think it would make sense to move the bit into it's own sub-paragraph (give it it's own sub-heading) and I suggest calling it "Perception of a flattened sky vault", after Schopenhauer's own words in his explanation in (the English translation of) his book. I'm gonna try and edit the article to do that now; please consider this as the accompanying explanation for that edit.

By the way, for those who are interested, here is a link to the entire book on Wikisource in English: [] Greetings, RagingR2 (talk) 10:17, 17 September 2013 (UTC)

See here These are marginal numbers [113] and [114].Lestrade (talk) 00:27, 10 February 2014 (UTC)Lestrade

In addition to my explanation above: I just finished editting the "explanations" section a bit and added a section title for Schopenhauer and one other section title. I also noted, while doing this, that the sub-section called "Angular size and physical size" provides sources whatsoever. Also, I wonder if it isn't redundant; maybe it's content is overlapping with the concent of the earlier explanations. So I think it's mainly confusing because right now it is prestented as yet another theory while it doesn't really offer anything new. I have left that bit in the article for now, but if someone else is going to delete it, they have my blessing. Unless any sources can be found for it, of course. Greetings, RagingR2 (talk) 10:33, 17 September 2013 (UTC)

A 'potential problem for the apparant distance hypotheses' ? I disagree.
Under the section 'apparent distance hypothesis', there is this section: So, there are sources for those statistics, four in fact. But are those sources also support for the claim that these statistics are a problem for the apparant distance theory? Because I don't think they are a problem, in fact they may just as well be seen as support for the 'succesful workings' of the illusion! I think there is a confusion here between conscious observation and subconscious observation. The way this section is written, it is stated as if the hypothesis (moon looks larger because it looks farther away) is undermined by the fact that a large percentage of people say (=consciously) that they don't think the moon looks farther away, but instead it looks closer. But of course, what people say will always involve their knowledge about the moon, and can of course not be seen separate from the illusion. After all, everyone who is used in such a survey is affacted by the moon illusion! So you might just as well say, of course they will say the moon looks closer and bigger; that is what the moon illusion does! But if you read Schopenhauer's theory which is sourced in this same section, it's not about what people consciously say or know, the moon illusion is about what the brain (subconsciously, or intuitively) *thinks* it knows. The moon illusion (at least in the 'apparant disctance' hyptothesis), works on a more fundamental level like most optical illusions do. The moon looks bigger because of optical cues that influence the brains understanding of the physcal world. This works on a deeper level, before knowledge and conscious thoughts come into play. So, the way I read it, these statistics may just as well be used as support for the fact that the moon illusion indeed exists and works. You might say even though their 'stated experience' ( = in a survey explicitly asking for their opinion) is that the moon low at the horizon looks closer, their 'demonstrated experience' is that the moon is further way when it is lower at the horizon, because intuitively our brains think that the sky has this 'flattened dome' shape, making the horizon farther away than the zenith, and by extension, also the objects which are at those positions respectively. Greetings RagingR2 (talk) 22:43, 8 February 2014 (UTC)
 * A potential problem for the apparent distance theory has been that very few people (perhaps about 5%) perceive the horizon moon as being both larger and farther away. Indeed most people (perhaps 90%) say the horizon moon looks both larger and closer than the zenith moon (Boring, 1962; Hershenson, 1982; McCready, 1965, 1986; Restle, 1970).

to hold a small object...

 * "A simple way of demonstrating that the effect is an illusion is to hold a small object (say, 1.4 inches or 36 millimetres wide) at arm's length (25 inches or 640 millimetres) with one eye closed, positioning it next to the seemingly large Moon. "

Why so big an object? The moon is about .5 degrees in diameter, which is about one third of a finger's width at arm's length. It can be better compared to an object that is about equal to its size (e.g. .5 cm) than to an object that is about seven times its size. --Neitram (talk) 17:44, 15 November 2016 (UTC)

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