Valo ja väri

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 valkoinen.

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.

Part of the Aura-Soma Thesis 2002, copyright © Anna Maria Pajarinen

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 permanently.

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.

Part of the Aura-Soma Thesis 2002, copyright © Anna Maria Pajarinen