Colour – The Spectrum of Science episode 2: The raw, early Earth had plenty of colour, but that canvas was about to be painted with a vast new palette – and the source of those colours was life.
We live in a world ablaze with colour. Rainbows and rainforests, oceans and humanity, earth is the most colourful place we know of. But the colours we see are far more complex and fascinating than they appear. In this series, Dr Helen Czerski uncovers what colour is, how it works, and how it has written the story of our planet – from the colours that transformed a dull ball of rock into a vivid jewel to the colours that life has used to survive and thrive. But the story doesn’t end there – there are also the colours that we can’t see, the ones that lie beyond the rainbow. Each one has a fascinating story to tell.
The raw, early Earth had plenty of colour, but that was nothing compared with what was going to come next. That canvas was about to be painted with a vast new palette – and the source of those colours was life. Green is the colour of the natural world and yet it’s the one colour that plants have evolved not to use.
The huge diversity of human skin tones tells the story of how humanity spread and ultimately conquered the planet. But the true masters of colour turn out to be some of the smallest and most elusive. Helen travels to the Great Smokey Mountains of Tennessee during the one week in the year when fireflies light up the night sky with their colourful mating display. And she reveals the marine animals that hide from the world by changing the colour of their skin.
Colour – The Spectrum of Science episode 2
Colour , is the characteristic of visual perception described through color categories, with names such as red, orange, yellow, green, blue, or purple. This perception of color derives from the stimulation of photoreceptor cells (in particular cone cells in the human eye and other vertebrate eyes) by electromagnetic radiation (in the visible spectrum in the case of humans). Color categories and physical specifications of color are associated with objects through the wavelengths of the light that is reflected from them and their intensities. This reflection is governed by the object’s physical properties such as light absorption, emission spectra, etc.
By defining a color space, colors can be identified numerically by coordinates, which in 1931 were also named in global agreement with internationally agreed color names like mentioned above (red, orange, etc.) by the International Commission on Illumination. The RGB color space for instance is a color space corresponding to human trichromacy and to the three cone cell types that respond to three bands of light: long wavelengths, peaking near 564–580 nm (red); medium-wavelength, peaking near 534–545 nm (green); and short-wavelength light, near 420–440 nm (blue). There may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a color’s colorfulness).
The photo-receptivity of the “eyes” of other species also varies considerably from that of humans and so results in correspondingly different color perceptions that cannot readily be compared to one another. Honey bees and bumblebees have trichromatic color vision sensitive to ultraviolet but insensitive to red. Papilio butterflies possess six types of photoreceptors and may have pentachromatic vision. The most complex color vision system in the animal kingdom has been found in stomatopods (such as the mantis shrimp) with up to 12 spectral receptor types thought to work as multiple dichromatic units.