h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

As Veronica Huston once remarked in context of some of Addams family work, "...and also, I smoke...".

*Angelica Huston



I used to have excellent vision but age has taken a toll. I could see very fine detail from a distance and I could also focus extremely close to my eye to see even finer detail. (I irritated a few teachers with writing as small as the ruled lines.) That's all gone now and I need glasses for near and far vision.

I don't think I had any broader spectrum sensitivity than others, but I did always feel I could sense UV better than most as I have to squint on many cloudy days without sunglasses. This could just be an aspect of having blue eyes. (Or maybe being a freckled redhead.)

I do still have better than average color acuity. This could simply be through my training as a photographer. I've taken the real world, physical version of this test. If you have a good monitor with acurate color rendition the on-line test is pretty good.

http://www.xrite.com/online-color-test-challenge

The first time I took this test under controlled lighting conditions, I only swapped two of the color sample caps. And that version had a few more color scales to sort.




Today, there was a story on NPR about color perception. I didn't catch the beginning of the story which had something to do with whether or not Homer was aware of the color blue. Apparently, if your language doesn't have a word for blue, you don't see blue, at least in the way we think of blue. So as an experiment these two scientists, possibly psychologists, married with a young child, they never referred to the sky as blue while teaching the child colors. They would label everyday objects and pictures as blue, but not the sky. Then one day the father points to the sky and asks his son what color it was. The child didn't answer. The question apparently made no sense to the kid. Maybe because the sky wasn't an object. Later, on another day with a bright blue sky, the father asked again. After a lot of thought, the boy said it was white, another time it WAS blue, then later it was white again. After a while, it was always blue though.

Apparently there is much more cultural influence on color perception than we might think.



Oh, and the dress was always blue and black (with hints of gold) to me. That one was obvious to me as simply a matter of whether the viewer thought the woman was standing in open shade or in the sunlight.

Thanks for the test, Baron Grim. I did't do too well, but fortunately I never had a job that demanded a much better score.

"Apparently, if your language doesn't have a word for blue, you don't see blue, at least in the way we think of blue" [Baron Griom]

That's a fascinating statement. Thank you for making it. There are scholars who have debated whether the ancient Greeks had much color perception. The closest they would come to describing colors would be metaphors like "the wine-dark sea."

We should, however, be careful in our statements about what 'science' knows or doesn't know on the subject of colour perception. Especially, apparently, the BBC science section. (I would nEVER believe anything that comes from the Discovery or History channels, either.)

This sort of behaviour will make a researcher tear their hair out:

http://languagelog.ldc.upenn.edu/nll/?p=18237

The story I heard yesterday was on Radio Lab. Here's the full episode. I plan on listening to this at work tomorrow.

http://www.radiolab.org/story/211119-colors/

Thanks. I love RadioLab.

Here is a plausible debunking of the "Greeks can't see blue" statement.

http://jayarava.blogspot.co.uk/2015/03/seeing-blue.html

(The link was contained in the article linked to by Dmitri)

It ends with the reminder that the Greek flag is white and blue.

Isn't it black and bronze?

That RadioLab programme I linked above was quite fascinating on that subject. It delves into this meme that the Greeks didn't see blue. This is a phenomenon that is observed well beyond the Greeks. Looking through ancient texts colors typically arise in the language with Black and White appearing first, then the colors typically run Red, Yellow or Green, violet then Blue. Blue is almost always last. One hypothesis is that it isn't any matter of actual vision, but utility. There's no reason for a word for a color until you can MAKE that color. Blue is rather rare in nature. Red pigments are everywhere, red clay for example. But blue pigments aren't. Most of the blue flowers we have are cultivated. So, maybe cultures just don't develop color names until they can make that color.

Then the host make the point that while it may seem that blue in nature is rare, that falls down when you look up. That's when the story turns to the boy I mentioned earlier, who wasn't taught that the sky was blue so the concept didn't seem to make sense to him, he just wouldn't answer at first and when he did, his first impression was that the sky was white.

Fascinating.

Not a lot of people know that the sun is white. They think it is yellow.

Not just white, but the definition, standard and source for white.

If the sun was a different temperature, our idea of "white" might be more red or blue than the 5500-6000°K we evolved under.

The sun is 'yellow' in the sense that its peak rate of emission is in the yellow band of the visible spectrum, fewer lower frequency red photons and higher frequency blue photons than 'yellow' photons in the peak emission band.

Its probably not a coincidence that yellow is the range in which chlorophyll absorbs most strongly, with some supplementary high absorption bands in the red and blue.

The 'green' of chlorophyll is due to the fact that light in that band is not absorbed and is either transmitted or reflected.

If you attempt to grow green plants under monochromatic green light they'll wither and die, unable to use it.

Yellow light isn't registered directly by the cones of the human retina.

Instead its in a range where the sensitivities of the red and green cones of the retina overlap, so that if an approximately equal number of red and green sensitive cones are stimulated simultaneously, the next layer of neural processing generates a perception of yellow.

This is why yellow appears the brightest of all the chromatic hues.

A similar mechanism obtains with cyan or sky blue, which is in a range where the sensitivities of the blue and green sensitive cones overlap, making cyan the brightest of the 'cool' colors.

Actually the sun's peak emission is in the green part of the spectrum.

"Here is a plausible debunking of the "Greeks can't see blue" statement."

Thanks for that, TC. In post 105, I was careful to say that there is a debate. The debate cannot have a resolution because the Ancient Greeks have been dead for thousands of years. No one can bring them back to life and test them for color perception. The most that can be said is that their language functioned without some words that might identify common colors. Rather than trying to say that they couldn't distinguish colors from each other, it might be wiser to think that they didn't see the differences as worth writing about. Maybe they thought there were more important things to write about?

Ah – but will sun-bleaching your clothes leave them whiter than white than when compared to a leading laundry detergent?

<BB<

I've heard that the whiter-than-white was achieved by a chemical residue which remained in the clothes and absorbed ultraviolet light, re-emitting it as white light. This meant that the white clothes actually did give off more white light than they took in.

Yep. This is why many fabrics glow under black light. These "optical brighteners" are also in some toothpastes. This is why many people's teeth glow like their clothes.