Free The Faber Book of Science by John Carey Page A

diving bell, and conversation with him enables Newton to draw imaginative conclusions about underwater colours:
    Mr Halley, … in diving deep into the sea in a diving vessel, found in a clear sunshine day that, when he was sunk many fathoms deep into the water, the upper part of his hand, on which the sun shone directly through the water and through a small glass window in the vessel, appeared of a red colour, like that of a damask rose, and the water below and the under part of his hand, illuminated by light reflected from the water below, looked green. For thence it may be gathered that the sea-water reflects back the violet and blue-making rays most easily, and lets the red-making rays pass most freely and copiously to great depths. For thereby the sun’s direct light at all great depths, by reason of the predominating red-making rays, must appear red.
    Newton’s theory that white light was not pure but a medley of different colours met with strong opposition. It seemed counter to common sense, which had long associated whiteness with purity and simplicity. Poets, however responded to the new colour-theory excitedly. The influence of the Optics flooded eighteenth-century poetry with colour. Alexander Pope’s ‘sylphs’ – fairy creatures who flit around a young lady’s dressing-table in his poem The Rape of the Lock – show clear evidence of Newton’s prismatic discoveries:
    Transparent forms, too fine for mortal sight,
    Their fluid bodies half-dissolved in light.
    Loose to the wind their airy garments flew,
    Thin glittering textures of the filmy dew;
    Dipped in the richest tincture of the skies,
    Where light disports in ever-mingling dyes,
    While every beam new transient colours flings,
    Colours that change whene’er they wave their wings
    Later, however, in reaction against eighteenth-century Enlightenment values, the Romantic poets condemned Newton for banishing mystery from the universe, and reducing everything to fact and reason. ‘Art is the Tree of Life. Science is the Tree of Death,’ proclaimed William Blake. John Keats agreed that Newton had ‘destroyed all the poetry of the rainbow by reducing it to prismatic colours’ – an opinion he versified in Lamia:
    There was an awful rainbow once in heaven;
    We know her woof, her texture; she is given
    In the dull catalogue of common things.
    Philosophy will clip an angel’s wings,
    Conquer all mysteries by rule and line …
    These Romantic outbursts suggest a profound ignorance of Newton, who was, in fact, acutely aware of the mystery of the universe. Colour itself, he points out in the Optics, is mysterious. What we call ‘colour’ in an object is merely ‘a disposition to reflect this or that sort of rays more copiously than the rest’, and the rays themselves are not really ‘coloured’, but set up a motion that, when it meets our eye, gives us the sensation of colour – ‘as sound in a bell or musical string, or other sounding body, is nothing but a trembling motion’. Why particular objects should reflect particular rays, and how they affect the eye to suggest colours, Newton found inexplicable.
    In the twentieth century Alfred North Whitehead rephrased this problem, and its implications for poets, in his Science and the Modern World :
    There is no light or colour as a fact in external nature. There is merely motion of material. Again, when the light enters your eyes and falls on the retina, there is merely motion of material. Then your nerves are affected and your brain is affected, and again this is merely motion of material … The mind, in apprehending, experiences sensations which, properly speaking, are qualities of the mind alone. These sensations are projected by the mind so as to clothe appropriate bodies in external nature. Thus the bodies are perceived as with qualities which in reality do not belong to them, qualities which in fact are purely the offspring of the mind. Thus nature gets credit which should in truth be reserved