The Wikipedia Wizards are working wonders with human colour perception.
According to the Carl Zeiss web site the visible spectrum “covers the wavelength spectrum between 380 nm and 780 nm.”
The visible area is the range of electromagnetic radiation that is visible to the human eye.
It covers the wavelength spectrum between 380 nm and 780 nm.
Zeiss – Spectrometer Modules For the UV to the NIR wavelength range
Back in 2004 the Wikipedia Wizards agreed with Carl Zeiss although they added the caveat that “400 nm to 700 nm” was “more common”.
The optical spectrum (visible light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye.
The optical spectrum is a composite, or mixture, of the various colors.
There are no exact bounds to the optical spectrum ; a light-adapted eye typically has a maximum sensitivity of ~555 nm (in the green).
Commonly the response of the eye is considered to cover 380 nm to 780 nm although a range of 400 nm to 700 nm range is more common.
The eye may, however, have some visual response at even wider wavelength ranges.
Nowadays the Wikipedia Wizards only mention a “typical” range of “390 to 700 nm”.
A typical human eye will respond to wavelengths from about 390 to 700 nm.
This restricted range quoted by the Wikipedia Wizards seems to be associated with their desire to make Indigo invisible.
Indigo is the “I” in the [old fashioned] “ROYGBIV” acronym that was taught at schools as an aid to remembering the seven colours of the rainbow.
Roy G. Biv, also ROYGBIV, is an acronym for the sequence of hues commonly described as making up a rainbow: Red, Orange, Yellow, Green, Blue, Indigo and Violet.
BBC Bitesize – Light waves
The colors change as the wavelength increases from violet to indigo to blue, green, yellow, orange, red and deep red.
NOAA – The Color of Clouds
The Wikipedia Wizards have magically reduced the rainbow to just six colours and made Indigo invisible by extending the spectrum range of Violet from 380-420 to 380-450 nanometres.
Violet (named after the flower violet) is used in two senses: first, referring to the color of light at the short-wavelength end of the visible spectrum, approximately 380–420 nanometres (this is a spectral color).
Violet is the color of amethyst, lavender and beautyberries.
It takes its name from the violet flower.
Wavelength 380–450 nm
Hex triplet #7F00FF
Indigo is a color that is traditionally regarded as a color on the visible spectrum, as well as one of the seven colors of the rainbow: the color between blue and violet.
Wavelength 450–420 (disputed) nm
Hex triplet #4B0082
By reducing the rainbow to just six colours the Wikipedia Wizards now only have to make Violet vanish when they cast their magic spells over the colours of the solar rainbow.
This new and improved magic rainbow of just five colours [i.e. Indigo invisible and Violet vaporised] enables the Wikipedia Wizards to claim that the sky is blue because short wavelength blue light is scattered more than longer wavelengths.
The sunlit sky is blue because air scatters short-wavelength light more than longer wavelengths.
Since blue light is at the short wavelength end of the visible spectrum, it is more strongly scattered in the atmosphere than long wavelength red light.
The result is that the human eye perceives blue when looking toward parts of the sky other than the sun.
The color perceived is similar to that obtained by a monochromatic blue of wavelength 474–476 nm mixed with white light, i.e., an unsaturated blue light.
Using the logic of the Wikipedia Wizards with the real seven coloured rainbow would cause the sky to be Violet/Indigo.
This five colour rainbow charade played by the Wikipedia Wizards is to misdirect you away from the full sky Daytime Aurora of blue fluorescing molecular Nitrogen.
Typical aurora spectral lines
Hydrogen, oxygen (O_2), and nitrogen in various forms (N_2, N_2+, N I, N II) provide most of the aurora colors according to this spectrum.
Credit: National Oceanic and Atmospheric Administration/Department of Commerce: Image ID: wea01029, Historic NWS Collection; Credit: Collection of Dr. Herbert Kroehl, NGDC
* Green – oxygen atoms 60-93 miles up (100-150 km)
* Red – oxygen atoms from 93-155 miles (150-250 km)
* Purple – molecular nitrogen up to 60 miles (100 km)
* Blue/purple – molecular nitrogen ions above 100 miles (160 km)
Technicolor Auroras? A Reality Check – Bob King – 14 October 2013
Blue “ionized molecular nitrogen” Auroras occur on the night side of the Earth “at the highest levels of solar activity” with fluorescence at “428 nm (blue) being dominant.”
Red: At the highest altitudes, excited atomic oxygen emits at 630.0 nm (red); low concentration of atoms and lower sensitivity of eyes at this wavelength make this color visible only under more intense solar activity.
The low amount of oxygen atoms and their gradually diminishing concentration is responsible for the faint appearance of the top parts of the “curtains”.
Scarlet, crimson, and carmine are the most often-seen hues of red for the aurorae.
Green: At lower altitudes the more frequent collisions suppress the 630.0 nm(red) mode: rather the 557.7 nm emission (green) dominates.
Fairly high concentration of atomic oxygen and higher eye sensitivity in green make green auroras the most common.
The excited molecular nitrogen (atomic nitrogen being rare due to high stability of the N2 molecule) plays its role here as well, as it can transfer energy by collision to an oxygen atom, which then radiates it away at the green wavelength.
(Red and green can also mix together to produce pink or yellow hues.)
The rapid decrease of concentration of atomic oxygen below about 100 km is responsible for the abrupt-looking end of the lower edges of the curtains.
Yellow and Pink are a mix of red and green or blue.
Other shades of red as well as orange may be seen on rare occasions; yellow-green is moderately common.
As red, green, and blue are the primary colours of additive synthesis of colours, in theory practically any colour might be possible but the ones mentioned in this article comprise a virtually exhaustive list.
Blue: At yet lower altitudes, atomic oxygen is uncommon, and ionized molecular nitrogen takes over in producing visible light emission; it radiates at a large number of wavelengths in both red and blue parts of the spectrum, with 428 nm (blue) being dominant.
Blue and purple emissions, typically at the lower edges of the “curtains”, show up at the highest levels of solar activity.
Ultraviolet: Ultraviolet light from aurorae (within the optical window but not visible to virtually all humans) has been observed with the requisite equipment, and otherwise invisible aurorae of this type were produced on a very small scale by certain HAARP experiments.
Infrared: Infrared light, in wavelengths that are within the optical window, is also part of many aurorae.
Therefore, it’s very reasonable to expect direct solar irradiance to create a full blue sky “ionized molecular nitrogen” Aurora [in the D Layer] on the day side.
The D layer is the innermost layer, 60 km (37 mi) to 90 km (56 mi) above the surface of the Earth.
Ionization here is due to Lyman series-alpha hydrogen radiation at a wavelength of 121.5 nanometre (nm) ionizing nitric oxide (NO).
In addition, high solar activity can generate hard X-rays (wavelength < 1 nm) that ionize N2 and O2.
Recombination is high in the D layer, so net ionization is low, and high-frequency (HF) radio waves are significantly damped within the D layer by collisions with electrons (about ten collisions every millisecond).
This is the main reason for absorption of HF radio waves, particularly at 10 MHz and below, with progressively smaller absorption as the frequency gets higher.
This effect peaks around noon and is reduced at night due to a decrease in the D layer’s thickness; only a small part remains due to cosmic rays
Conversely, it’s highly unreasonable to dismiss the concept of a full blue sky “ionized molecular nitrogen” Aurora on the day side without good reason.
Before arriving at a decision it is also worth considering the remarkable observation that 78% of the Earth’s atmosphere [i.e. Nitrogen] is not associated with any of the Major Fraunhofer Absorption Lines whilst Oxygen [amounting to almost 21% of the Earth’s atmosphere] is associated with Bands A and B which are now classified as “telluric lines”].
Nitrogen is a chemical element with symbol N and atomic number 7.
On Earth, the element forms about 78% of Earth’s atmosphere and as such is the most abundant uncombined element.
The element nitrogen was discovered as a separable component of air, by Scottish physician Daniel Rutherford, in 1772.
In 1802, the English chemist William Hyde Wollaston was the first person to note the appearance of a number of dark features in the solar spectrum.
In 1814, Fraunhofer independently rediscovered the lines and began a systematic study and careful measurement of the wavelength of these features.
In all, he mapped over 570 lines, and designated the principal features with the letters A through K, and weaker lines with other letters.
Modern observations of sunlight can detect many thousands of lines.
About 45 years later Kirchhoff and Bunsen noticed that several Fraunhofer lines coincide with characteristic emission lines identified in the spectra of heated elements.
It was correctly deduced that dark lines in the solar spectrum are caused by absorption by chemical elements in the Solar atmosphere.
Some of the observed features were identified as telluric lines originating from absorption in oxygen molecules in the Earth’s atmosphere.
The Fraunhofer lines are typical spectral absorption lines.
In other words:
If atmospheric Nitrogen emits visible light at night then why doesn’t it emit [or absorb] light when it is exposed to the full power of the Sun during the day?