Talk:Mirage

Highway Mirage

While closely related, and they certainly should be linked, I see two seperate articles on Mirage and Highway mirage as making sense. I grew up seeing a lot of highway mirages in the Oregon desert. dino 20:07, 19 April 2006 (UTC)[reply]

They're the same phenomenon! Sometimes I just can't understand why people want to keep articles separate (note spelling). —Keenan Pepper 21:24, 19 April 2006 (UTC)[reply]

Yes, there is absolutely no reason to have a separate article on "highway mirages". It is exactly the same phenomenon as a desert mirage. The only difference is that it happens to occur on a highway. --Srleffler 12:03, 26 May 2006 (UTC)[reply]

I moved the material Dino added from the former highway mirage article to a subsection of "inferior mirage", where it belongs. The material is completely redundant with what is already here, but it does explain the phenomenon in a nice, simple way. The redundancy is still annoying, though. Maybe later I'll look at incorporating the nice simple explanation into the main "explanation" section.

BTW Dino: '#' section references don't work on redirects.--Srleffler 21:39, 30 May 2006 (UTC)[reply]

obnoxious mathematics

Srleffler, you changed the normal adiabatic gradient from +1 to -1°/100m. Although more correct, now the statement: smaller than -1° is confusing. Mathematically speaking -1.1 is a valid solution, but intuitively speaking people will think of -0.9 etc. (In fact the latter is meant). Please think about some rewording.

Likewise ±3 is mathematically speaking +3 or -3 (as the solution of the square root of 9). ~3 for 'circa 3' would be better, as was intended. But maybe less known. Some rewording?

Oh, and thanks for general cleaning up my English --Tauʻolunga 20:02, 26 May 2006 (UTC)[reply]

I agree with you about "smaller than". I was hoping this would be less confusing than "less than" (since smaller might imply magnitude rather than value), but apparently this doesn't work. I changed it to "about -1". If you have a more precise value, substitute it in.

Where I wrote ±2, I really meant +2 or -2, not "circa 2". Clearly it is the magnitude of the gradient that matters, so either +2 or -2 is sufficient to produce a mirage.--Srleffler 22:12, 26 May 2006 (UTC)[reply]

I see. However the values quoted were for an inferior (-) image only. Values for the superior (+) image were not given. But I reckon that we can keep it like this until someone comes with additional data. --Tauʻolunga 00:56, 31 May 2006 (UTC)[reply]

Word Origin

Mirage is called "Mareechika" in Sanskrit (Ancient Indian) language. Can someone tell me whether there is any relationship between these two? If thats true, it might have originated from Indo-Aryan word rather than from something like 'Mirror' !—The preceding unsigned comment was added by Shreeshiri (talk • contribs) .

The SOED and Chamber's Dictionary of Etymology agree that it comes from the French mirage, from mirer "look at", from the Latin mirare "wonder at". It's related to the Sanskrit smayas "surprise, astonishment", but not to mareechika as far as I know. —Keenan Pepper 23:21, 16 June 2006 (UTC)[reply]

Total Internal Reflection

Here's a bit of "original research." I've always had niggling doubts about mirage explanations. Mirages to me appear suspiciously similar to Total internal reflection. At just this moment my doubts solidified: as light moves from a dense medium to a less-dense medium, light is refracted as its angle changes proportially to the difference in refractive indices... but the angle never becomes negative. Refractive transitions between media can only bend light, not reflect it. However, if light leaves a dense material and enters a rarified material at a glancing angle, and this angle is less than the Critical angle of total internal reflection, the light will be 100% reflected. Therefore, since refraction only causes bending, while TIR causes reflection, hot-road mirages are an example of internal reflection. But I've never seen this explanation anywhere. I suspect that the standard refractive-bending explanation of mirages may be a galloping myth, an "infectious textbook misconception." How could we decide this issue? Easy: if light glances off the heated roadway at more than the Critical angle, the light will split into two paths: a weak reflection and a strong refraction. As the incident angle decreases, suddenly the reflection goes to 100% and the refraction goes to zero. If such a thing occurs with roadway mirages, then those mirages are caused by internal reflection phenomena and not by simple bending of light as is usually explained. I found a reference which points out that if mirages were refractive, they would be rainbow-colored because of dispersion. Since such dispersion is not seen, and mirages appear to be 100% mirrors, they are internal reflections and not refractive bends. --Wjbeaty 06:58, 30 October 2006 (UTC)[reply]

That does make sense, intuitively. I found several pages which seem to support the idea of mirage as TIR, for instance: [1], [2], and [3]. It's been way too many years since my last optics class -- so I'll refrain from actually attempting to introduce this concept into the article. --Dfred 21:19, 24 February 2007 (UTC)[reply]

TMI - Too many images

The article seems to have become a dumping ground for every image of a mirage there is, and there are too many images of mirages. I've put most of the additional images into galleries at the end of the article, but eventually most of them should be removed and the most clear, understandable images remain. -- atropos235 ✄ (blah blah, my past) 03:24, 7 June 2007 (UTC)[reply]

Yes, these images should be moved to http://commons.wikimedia.org/wiki/Mirage and removed from this page. The article needs 2 or 3 images of mirages at most, not 50. Kaldari (talk) 00:18, 12 March 2008 (UTC)[reply]

It would cut down on the inferior mirage images to remove the ones that aren't inferior mirages at all. The three that look over water are superior mirages, and may as well be the first to be removed because they are mislabeled. Remember - hot surface = inferior, cold surface = superior - as far as mirages are concerned. See the image I posted from the Black Rock Desert for an example of an inferior mirage. If there are no objections, I'll remove the mislabeled images from the gallery. Ikluft (talk) 13:19, 3 April 2008 (UTC)[reply]

This article is predicated on a falsity.

Cold air is denser than warm air, and has therefore a greater refractive index.

Material density is not the same thing as optical density. This is non sequitur. The refractive index of a medium does not depend on its material density, as in its mass divided by its volume. Moreover, more dense media do not necessarily have a greater refractive index than less dense media.

If the passage means that cold air is more optically dense than warm air, it must explain why, since there is no obvious reason.

--76.224.90.253 18:27, 22 September 2007 (UTC)[reply]

Let me elaborate.

The reason people think that refractive index depends on density is because they have read somewhere that refractive index depends on optical density, and that the refraction occurs when light changes media from one that is "optically rare" to one that is "optically dense" or vice versa. This is false in at least two different ways, the least significant of which being the fact that "optical density" is commonly used to refer to something else entirely, not related to refraction at all. That has no bearing on the incorrectness of this article.

I can think of any arbitrary number of media which can be arranged simultaneously in order of increasing density and decreasing refractive index. I can think of any arbitrary number of media with equal density and unequal refractive index. I can think of any arbitrary number of media with equal refractive index and unequal density.

The provided explanation is wrong, period. This does not represent a misunderstanding by scientists. Merely by Wikipedia contributors over compounded misuses of the word "density".

Also, I see no reason for this article to attempt to explain what has already been explained correctly in the article on refraction -- which does not use the words "dense" or "density" at all, not even once.

--76.224.90.253 22:53, 22 September 2007 (UTC)[reply]

Not an optical illusion?

Can someone explain why the article states that mirages are not optical illusions? There appears to be water on the road; it's not actually there. That's an illusion, and it's due to an optical effect. Hence, optical illusion. It's not a cognitive optical illusion (that is, an effect created by the brain), but that doesn't mean it's not an optical illusion. Benizi (talk) 20:50, 4 February 2008 (UTC)[reply]

Based on the optical illusion page, I described a mirage as a "literal optical illusion."66.253.237.191 (talk) 07:43, 14 May 2008 (UTC)[reply]