Talk:Moon illusion

message: 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)
thread_title:  Non-possiblities 

message: 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)
thread_title:  What a mess this has become 

message: 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)
thread_title:  Comparison Photo 

message: 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)
thread_title: Discovering the Illusion

message: 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)
replies: text:  I think your post is a hoax. You cannot be serious!76.113.105.186 (talk) 05:38, 23 October 2010 (UTC)
thread_title:  Illusion? 

message: 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)
thread_title:  This article confuses me 

message: 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)
thread_title:  What on earth has happened to this article? 

message: 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)
thread_title: Reply to "What has happened?"

message: 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)
thread_title:  Pruning too extreme 

message: 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)
thread_title:  Is relative size hypothesis a particular case of the apparent distance hipotesis? 

message: 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)
thread_title: No, it is a serious mistake to think the two theories are the same.

message: 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)
thread_title: Expand the illusion

message: 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)
thread_title:  "Point of reference" theory 

message: 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)
thread_title: Is the moon the real issue here?

message: 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)
thread_title:  Angle of regard hypothesis 

message: 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)
thread_title:  Ptolemy ? 

message: 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)
replies: text: 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)
thread_title:  Strange Illusion - Related? 

message: 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)
replies: text: 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)
thread_title:  Watching the moon upside-down 

message: 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)
thread_title:  Schopenhauer's explanation warrants it's own sub-section? 

message: Under the section 'apparent distance hypothesis', there is this section:
* 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).
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)
thread_title:  A 'potential problem for the apparant distance hypotheses' ? I disagree. 

message: :"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)
thread_title:  to hold a small object... 

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