According to a LiveScience article, Phil got it only partially correct. This is the rest of the story, or at least More of the story. Check it out.
http://www.livescience.com/forcesofn..._blue_sky.html
And a partial quote:

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How many times have you been about to grasp the truth when somebody else suddenly yanked it out of your reach?

I don't see anything that would warrant the claim, "the answer, explained fully for the first time in a new scientific paper, is in the eye of the beholder."

Perhaps the idea that violet plus blue yields blue as a metamer, maybe - not that I know better. It is well known, however, that color is determined from the spectral irradiance that enters the eye and the spectral response of the eye. There are other oddities regarding eye response, too.

Our response in violet is very weak and the sun's radiance is stronger in blue than violet, too. Further, the energy of each "violet" photon is higher than the others. This means that even if the level of intensity (wattage) for violet was the same as blue, the cones would register more blue since there would be more "blue" photons. It would not be a dramatic difference, however. The first two points are the key factors.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

naw... Phil got it all wrong
I certainly hope that helps clear this little question up...

I don't think I understand your comment here. What is it you are questioning? "...explained fully" , "for the first time", or "is in the eye of the beholder"? If you are taking issue with only the part of the article I quoted, I think the claim is warrented by the details in the rest of the article which I did not quote here.

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How many times have you been about to grasp the truth when somebody else suddenly yanked it out of your reach?

There was nothing new under the sun I found in the article with the exception of the metamer suggestion of adding violet to blue to obtain blue (that seems a little odd, but I may have misunderstood it).

There are several nit errors in the article,too. If you like I'll cover them, but I just happen to have a skunk in the back yard at the moment. My dog lost the battle, and its now my turn. I'm not kidding, either.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

It seems to me that it's like adding x-rays to the explanation--why violet instead of x-ray? We can't see x-rays either, their wavelength is even shorter than violet's.

Yes. That is the issue and the point Smith may be conveying.

But, this is so well known, that I am surprised the article states that his paper is the first time anyone has presented the full picture. The response characteristics of the eye and the spectral irradiance of the sky, and the reason for it, have been known for a long time. If Smith's work is the first, we have been long overdue considering how much was already known. I did a Goo1 (level 1 Google search) and could not find a paper that incorporates all of this. Perhaps the originality claim is correct. I still doubt it.

About two years ago, or so, I read a related magazine article written by an astronomer who explained how the eye works and claimed the sun was really a green star. I was highly intrigued. Then came the BA's book, and I've been stuck chasing the sun's color ever since. I thought the article discussed the blue sky, too. If so, his work would have preceeded Smith's.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

We do see "violet" light, but it activates only our blue-sensitive cones (and not as strongly as does blue light). Sky-blue light also activates our green-sensitive cones very slightly. What we see as sky-blue contains a little bit of green (but only in the way we perceive it).

You know how the sky has different shades of blue? Well, a part of that is determined by differences in the spectrum of light that actually enters our eye. Where the sky is an intense, deep blue, that is mostly the shorter-wavelength stuff. Where it looks a bit less intense (and not just the "washing-out" effect caused by looking through more atmosphere, as the sky overhead can appear different shades of blue at different times of day and on different days), there are some slightly longer "blue" wavelengths involved as well.

This has been known for decades, so I do not quite see what this new discovery is meant to be.

Anyway, I thought there were two effects at work - one scattering (absorption / re-emission at different intensities for different wavelengths) and one refractive.

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The quarrelsome oarsmen were rowing,
The great violinist was bowing;
But how is the sage
To tell, from the page:
Was it pigs or seeds that were sowing?

Yes, perhaps it's time for a graph of our responses of our three types of cones. [The blue end coloring looks correctly aligned to wavelength to me, but not the red end.]

[Added: notice how insensitive our cones are to violet.]

I do not quite follow this. Are you saying a little more green exists overhead at certain times of the day to cause blue to lighten, regardless of other effects? That makes some sense near noon time, I suppose.

How do you see refraction contributing?

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

Indeed. The whole story has been around for a long time, and is covered as such in many standard textbooks. Craig Bohren gives a succinct summary (Section 2:3 in the linked article, including mention of metamerism). John Naylor addresses the eye's sensitivity as it affects the blueness of the sky in Out of the Blue, as does Marcel Minnaert in Light and Color in the Outdoors: and those are just the first three reference sources I lifted off the shelf.

Indeed, Phil seems to have done more background research than Glenn Smith, since in his section on the blue sky (Chapter 4) he explains why the sky doesn't appear violet, and mentions that: "... your eye is more sensitive to blue light than it is to violet."

I can only guess that Smith restricted his browsing to basic physics texts, which were trying to teach about scattering, rather than specifically about the blue sky.

Grant Hutchison

You must show us a picture of your library someday.

Arnold Bussick's paper was written about a year earlier than Smith's covering the eye's response contribution and light scattering, even Einstein's Critical Opalescence approach was briefly introduced.

The hype of being first, of course, might not be Smith's fault.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

Okay, guys, Thanks for all your responses and information re my original post here! Much appreciated. I was not aware Phil had indeed covered this in his book. I haven't read it. I made the incorrect assumption (hunh, imagine that!) that since the issue of metamers and how the eye percieves different wavelengths of light wasn't mentioned in his article in the Misconceptions page of this site, that perhaps he hadn't been comprehensive enough.

Live and learn! Thanks again to all! Hopefully I will continue to live some more and learn some more,... and not make those annoying assumptions as often - I don't figure I can eliminate them altogether.

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How many times have you been about to grasp the truth when somebody else suddenly yanked it out of your reach?

I think you'll find we all enjoyed it. So, thanks. The media(?) claim that the article was a first is "bad astronomy" and that is what we go after, of course. We've had some interesting colorful conversations regarding this topic; I'm sure we'll have more.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

Well, now, you have to read the book to make up for it, don't you think? It's only polite!

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Gillian

"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"

"You can't erase icing."

"I can't believe it doesn't work! I found it on the internet, man!"

Metaphorical gold is another subject.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

Interesting discussion here, but the first thing that comes to my mind is - we may well see the sky as blue, but how about our animal neighbours we share this place with?

How do they see the sky? Insects for instance, is it a blue expanse they glimpse, or some sort of yellow wonder? Or is it in various shades of gray?

It would be interesting to know how other animals perceive the most common sight on the planet.

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BugMeNot A portal to bypass free-site registration.

"All truth passes through three stages. First, it is ridiculed, second it is violently opposed, and third, it is accepted as self-evident." Arthur Schopenhauer - renowned 19th Century German philosopher.

You can Google for quite a variety of information regarding animal vision.

Surprisingly, birds, for one, have four types of color cones compared to our three. Also surprisingly, for what little I've seen, these color cones have sensitivies independent of each other. In other words, each wavelength of light can only be detected by one of their cones, not more than one. This gives them much better input for their color processing. My guess is they see many colorful objects slightly different but probably with greater vividness.

Deer, at least whitetail, have only two color cones, but they have larger eyes with other special features to enhance vision. One color cone may even allow vision in the near UV range. After learning this, I think of how funny it is that deer hunters think they are able to climb in deer blinds unnoticed by the deer because they, the hunters, think the sky is dark, but to the deer, the sky is relatively bright.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

I didn't know that was what deer hunters thought, I thought they climbed up to the blinds because deer didn't notice them up there.

That is true but they assume that since it is dark when they climb up, then the deer can't see them. I am a hunter and always assumed we risked injury, freezing, and snake bites for that purpose.

IIRC, deer can not see orange or light of greater wavelength, so although hunters now wear orange primarily because they don't want to get shot by other hunters, I think many hunters also think the deer can't see them. Yet, any object the eye can not see will look black, so a deer will see hunters as if they were wearing black, which could stand out like a sore thumb.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.