Is violet found in the rainbow?

We are taught that Richard Of York Gave Battle In Vain and for this gem we have to thank Isaac Newton who also had a whacky theory of how colour related to music. Whilst we can credit Isaac with some understanding of colour theory, his seven named spectral colours have been grossly misused over the centuries since.

Isaac's colour wheel

And so Johnny is taught in school that the rainbow has seven discrete colours. He is also falsely taught that the primary colours are red, blue and yellow. As a child I quickly learned from experiment the falsehood here. You try getting a decent purple by mixing red and blue paints! It would be more correct to say that the primary colours for additive mixing are red, blue and green (but c.f.) and that the colours you get from mixing these in equal proportions, aka secondary colours, namely yellow, cyan and magenta, are for this very reason the primary colours for subtractive (paint) mixing.

In our school room here we have a colourful set of of containers which I have pictured below, Which of the container colours shown are not found in the spectrum of white light?

A friend JHA recently gave an dissertation on blue and red, as in the colours of the rainbow. He excluded purple and did not mention violet thus implying that the ends of the visible spectrum are red and blue. I consider this a gross injustice, I feel as though I have been robbed. Whilst I can do away with indigo because the truth is that the spectrum is a continuous variation in colour, to say the rainbow ends in blue is a blatant lie. But the truth of the matter is not so clear. I thought JHA would go on to talk about green as the third "primary colour" and thus disprove the law of the excluded middle but the point he was making was somewhat different. But whatever he was talking about, he very definitely did not mention spectral violet.

So what is the truth? All sources agree that human eyes are trichromatic and thus possess three types of colour sensor or "cones" which have peak spectral responses around blue, green and red, and this is why colour TV and film can reproduce most colours using pigments of these colours aka primary colours. Although some folk, 10% of men I am told, only have two types of cone and are thus "colour blind". There is even the suggestion that some women might even have a forth type of cone which I regard as wholly unfair.  So far so good.  But hereafter theories differ.

There are those who deny that there is a problem at all. Until I hear him recant I must place my friend JHA in this category. For such people violet cannot exist in the rainbow.

Some say that the the "blue" cone is a misnomer because it actually has peak response to what we call violet spectral light. Spectral light of slightly longer wavelength actually tickles both the violet cones and to a lesser degree the other cones, and this combination we perceive as blue. And thus the sky is actually violet.

Others (and here) say that in fact the "red" cones have a secondary response in the violet area and thus light of this wavelength tickles both blue and to a lesser degree red cones and we perceive this mixture as violet.

Both parties agree that the eye perceives other mixtures of red and blue as variations of the purple / violet / mauve / magenta colours some of which are rather poorly defined.

In the second and third theories violet is definitely a spectral colour as distinct from blue, so that the only reason scientists might talk about the blue and red ends of the visible spectrum is because blue is an easier concept than violet. After all the first meaning of the word is a small wild flower.

One more (at least!) point that needs to be made is that, even in the rainbow, we are typically not looking at pure spectral colours, by which I imply monochromatic light. You'll get a better sensation of monochromatic light aka pure saturated colour by looking down a spectrometer, a device that splits light into a rainbow of colours e.g. using a prism but uses lenses and a slit to ensure that the eye is looking as only a very narrow angle of the emitted spectrum. As most of us do not have access to a spectrometer, try looking directly at a prism splitting white light. A chandelier crystal will do.

Colour film and TV can never do full justice to the eye's ability to see colour. Indeed the eye itself can never do full justice to the colours actually implicit in the spectrum. In either case the issue is firstly that the eye is trichromatic and secondly that the red, green and blue cones each respond to a broad range of colours and thus, apart possibly from the extreme ends of the visible spectrum, any particular spectral colour is bound to stimulate more than one type of cone and thus results in reduced saturation. This effect is progressively more evident as you move away from the centre of an oil film spectrum as captured in my recent photo.  Here you will see colours verging on brown, a colour no-one to my knowledge has ever claimed was in the rainbow.

The evils of light

I know I've posted about light pollution before, but the other day at lunch the two women sharing my table were lamenting how hard it was to see along the road at night now that the neighbours had not had their outside lights on recently. I could hardly help myself interjecting how, for me, such lights actually made it harder to see. One of them said it was amazing when I pointed out I could see better without the lights.  Does this mean my visual purple is much better than average? I can hardly believe this. This morning I was taking my breakfast at around 0730 as it was starting to get light outside. Quite light enough for me to consume my cereal and tea. Shortly after I am joined by another community member and, wham, on goes 6 glaring ceiling spot-lights. Why? I asked - because it's dark and I cannot see, he says. Can this really be true? Do They really prefer the harsh, brilliant artificial light to dawn?

And so I was please when this morning's BBC-news offering included this article listing various evils associated with increasing light pollution across the globe and writing "Human vision relies on contrast, not the amount of light, so by reducing contrast outdoors - avoiding glaring lamps - it is actually possible to have improved vision with less light."

The Kings River

Through king Turlough's land I flow

Snakelike, shaping as I go

Upon my bed rest ancient stones

Washed crystal clear, as my body runs

Changed to shine in different forms

When kissed by rays of golden sun

Sparkling natural gems are born

I earthly years some say I'm old

Some shy from me when summer's gone

For fear of catching winter's cold

Great pity them, for missing out

On my hypnotic tranquil sounds

Oh come, sit down by my side

And hear me sing, in beautiful tones

Songs of beauty old and new

I am a river fit for the king

Majestically my waters flow

Forever on in timeless mode

Johnny Carroll, October 2017

Johnny, a friend of mine, is into poetry in a big way. He claims to write a poem a day, or more, a feat that is quite alien to me. Poetry rarely tickles my fancy but this one caught my ear mainly, I suppose, because it is about something I love.  Naturally I wanted to find out more about the poem's allusions.

Doubtless the king in the first line is Tairrdelbach Ua Conchobair aka Turlough Mór O'Connor, King of Connacht (1106–1156) and High King of Ireland (ca. 1120–1156). I can, however, find no evidence that the name "Kings River" refers to this king in particular, although there is a Turlough Hill close to its source. But the hill was named Turlough quite recently and in any case the name is common and means a low-lying area which becomes flooded in wet weather, a description that could apply to a large percentage of Ireland. That's OK, I'm not complaining - I don't mind a bit of "poet's licence".

As far as being "crystal clear" the river is, as most are in this area, peaty brown but is otherwise clear and with a quality of "pristine nature" as testified by this report by the EPA. And I love to swim in it and clamber on the many rocks it flows around.  In the summer, that is.

I thoroughly identify with "great pity them" - I wonder that so few people really appreciate the Kings River. Spurred on by this poem I have made a mental note to do more exploring next summer (if we have one) like starting at Ballinagee bridge and rock jumping all the way to its source.

In the unlikely event that my reader is as besotted with Kings River as I am, the best mapping I can find is by Bing (much better aerial photography than Google maps in this area). Here you will see that the source of the river is on the western slope of Tonelagee towards Stoney Top.

Convection run

My route, 9.84 miles

Saturday afternoon run in between convention meetings, steady light rain but fairly mild (about 9'C) and the lake fairly low at the moment.

Access to the lake close to Poulaphouca

Loch Ness has nothing on this!

Strengthening works along this section close to the N81

Then back along the Blessington Greenway, across the Baltyboys bridge then along the lake shore to the Valleymount bridge.

On the road back home - superb example of interference

Community is...

... hosting a convention once a year.

Although our convention is somewhat smaller than this!

Folk visit from far and wide and our home is inundated for a while. I keep telling myself it is good to be sociable, good to share, but am not sure that my alter ego has got the message yet.

Convention is a time to get together, a time to re-focus, a time for God to speak. I hope so.