Näkyvä valo ja sen myötä värit ovat vain pieni osa auringosta peräisin olevaa sähkömagneettista säteilyä,
joka jaotellaan aallonpituuden mukaan seuraaviin osa-alueisiin: radioaallot, mikroaallot, infrapunasäteily,
(näkyvä) valo, ultraviolettisäteily, röntgensäteily ja gammasäteily. Luonnollinen valkoinen valo eli
sähkömagneettisen spektrin se osa, jonka silmät ja aivot ymmärtävät valoaistimuksena, sisältää jokaista
värisävyä vastaavan, oman aallonpituutensa. Valo voidaankin jakaa esimerkiksi prismalla jatkuvaksi spektriksi
eli kirjoksi, jossa värit sijaitsevat tietyssä, aallonpituuksien (350-700 nanometriä) mukaisessa järjestyksessään.
Pisin aallonpituus on punaisella (620-780nm) ja lyhin violetilla (400-430nm) värillä. Parhaiten ihmissilmä näkee
keltaista tai kellanvihreää valoa aallonpituudella 555 nanometriä.
Avaruus imee itseensä kaikki auringon lähettämät sähkömagneettisen säteilyn laadut, joten näemme avaruuden
mustana. Valon jatkaessa matkaansa maapallon ilmakehään, jakautuu se ilmakehän sisältämään vesihöyryyn, jonka
johdosta taivas näyttää silmissämme siniseltä. Näkyvän valon kohdatessa tietyn esineen osa valosta imeytyy sen
molekyylirakenteeseen ja osa heijastuu esineen pinnasta edelleen. Näin kohteen pinnan ominaisuudet vaikuttavat
siihen, mitä neutraalin vaalean valon aallonpituuksia esine imee itseensä ja mitä se heijastaa. Aistimme itseensä
kaiken valon imevän esineen mustana ja vastaavasti esine, joka heijastaa kaiken näkyvän valon, on väriltään
Ihminen aistii valoa ja sen myötä värejä silmän pohjaosan verkkokalvolla sijaitsevilla sauva- ja tappisoluilla.
Sauvasolut aistivat valoisuuden, ne ovat tärkeitä muun muassa hämäränäölle. Aistinsoluista tappisolut taasen
reagoivat väreille, kukin tappi tiettyyn aallonpituuteen. Näköreaktiota ohjaa eteenpäin sauva- ja tappisolujen
sisällä olevien molekyylien liike-energia. Valoinformaatio etenee sähköisenä impulssina näkörataa pitkin aivoille,
jotka muodostavat viestien laadun ja määrän perusteella mielikuvat eri värisävyistä.
The nature of light and colour as understood by Western science
Theories about visible light and its connection with colour have been expressed since the days of Plato,
Hippocrates and Aristotle, who presumed that beams of light depart from the human eye. One can glimpse this
field of light and colour by looking at some of the names, leading to the famous Isaac Newton: Aurelius Cornelius
Celsus, Pythagoras, Al-Haytham (965-1038), Robert Grosseteste (1168-1253), Paracelsus (1493-1541) and Galileo
Galilei. In 1666 Sir Isaac Newton passed light through a prism and formulated a new, revolutionary theory: white
light is itself made up of all the rainbow colours. He considered light to be composed of particles emitted by
luminous bodies and was the first one, who divided light into the seven colours of the spectrum. Newton's Light
theory was published in 1704 and his particle theory dominated science until the 19th century, when it was replaced
by the wave theory of light.
However, it was already in the late 17th century, when Newton's contemporaries, Christian Huygens and Robert
Hooke, pointed out the wave theories of light. Huygens presented a theory where the wavemotion of light is spreading
in the omnipresent ether and the scientists all over the world divided into two groups. Wave theorists had
complicated debates with the emissionists, who belived light to be a sequence of rapidly moving particles subject to
forces exerted by material bodies. Strong support to Huygens wave theory gave a clever scientist Thomas Young, who
studied diffraction and interference of light in 1803. Further contributions were made by many other reseachers,
among them A.J. Fresnel, who showed that light is a transverse wave.
Experiments carried out by J.C. Maxwell, A.A. Michelson, E.W. Morley, M. Planck and later on by A. Einstein led
the research to a new understanding of the nature of light. Michelson and Morley made the classical experiment with
an equipment called interferometer in 1881 which measured the speed of lightbeams with mirrors. The result, the speed
of light is constant, confused other scientists for decades until 1905 when 26 years old Albert Einstein wrote a
thesis to earn his doctorate from the University of Zurich, where he suggested a new physical point of view. Based on
Max Planck's quantum hypothesis he described the electromagnetic radiation of light and proposed the special theory
of relativity. The motivation for the Nobel prize to Einstein in 1922 was based on his discovery of the law of the
photoelectric effect. He drew the conclusions that both the concept of waves and the concept of particles in the light
heat bath in a cavity are called for and light is composed of the lightquantums called photons which have specific
energy and impulse.
Today, in the beginning of a new century, Quantum physics offer yet another solution to the wave- particle duality
theory. In the new theory it is said that an energy particle has particle-like and wave- like properties, but it is
neither of the two. B. Hoffman called this new entity a wavicle, but it is still difficult for us to achieve a clear
understanding of the nature of a wavicle because this object is very remote from our present experience that relates
to material objects. We are the children of the light and at this extent we have to use terms like time, gravity and
energy in order to observe the world around us. The truth however may be found from other dimensions and realities,
everything is here and now.
The nature of light and colour as understood by philosophy - mystical or otherwise
The German poet and nature scientist Johann Wolfgang von Goethe was inspired to research colour and light while
walking in the nature under the blue sky and admiring the colourful reneissance paintings in the early 19th century
Italy. This true genious felt that the best way to approach colours as physical phenomenons was through nature and he
devoted forty years of his life to these studies, testing the accuracy of Isaac Newton's experiments with a prism,
creating an advanced colour theory and publishing several of his discoveries.
Goethe classified colour into three groups: physiological, physical and chemical. The first part, the
physiological colours, form the basement of his colour theories, they are the colours that human eye makes up.
These are the colours closest to the human being since they are created by ourselves. The physical colours are
of more permanent character than the physiological, they are experienced through more or less transparent
substances or surroundings which themselves are colourless. The last category and the lowest level in Goethes
colour hierarchy, the chemical colours, are the most far away from the human being since they belong to an object
The interesting tests Goethe made with the prism, resulted the construction of a new colour circle. This
circle includes the red, blue and green together with the additional indigo, magenta and yellow. The left part
of the colour circle is where the warm colours of the day are, the yellow part. On the right side we find the
blue colours, the cool colours of the night. These observations also summarize the natures polarization theory
Goethe demonstrated: yellow colours are created when darkness meets light with light as background, while blue
colours are created when darkness meets light with darkness as background.
As a philosophical poet and admirer of the nature, Goethe also covered with a similar explonation the beautiful
burning sunsets. When the sun is at its summit, we see the white sun appearing yellow because the sunlight hits the
particles of the atmosphere with the light of the sun as background. When the sun sets, the angle at which the light
hits the earth makes it pass a thicker layer of particles of ash and coal which results in a redder colour.
Not until the middle of the 20th century Goethes work as a naturalist attracted understanding and appreciation.
His colour theories are not considered to be descriptions of the light as a physical form but rather psychological
studies how the human beings sense colour and light. His illustrative material between philosophics, mathematics,
natural history, melodics and colour theory indicate how colour affects the human senses and ethics. Even today his
work on the subject continues to unfold.