Sir Isaac Newton

Posthumous son of a Lincolnshire farmer, Isaac Newton (1642-1727) invented machines even as a boy. He was already experimenting and making important discoveries in optics as an undergraduate, and in 1667, at the age of 25, he was elected a fellow of Trinity College, Cambridge.
Although he wasn't particularly stimulated by his colleagues, Newton's mind was constantly engrossed in mathematics, physics and astronomy at the highest possible level.

Newton was to become a most eminent physicist, mathematician, astronomer, natural philosopher, alchemist and theologian. He has often been acclaimed the greatest scientist ever. It was Newton who revealed that all earthly objects and celestial bodies are governed by the same laws of planetary motion and his theory of gravity. His Philosophiæ Naturalis Principia Mathematica  (published in 1687) describes the three laws of motion and universal gravitation. It is still considered to be one of the most important scientific books ever written.

He often wrote his theories and conclusions in Latin, then still the international language of sciences. But as the excerpts from the letter to the Royal Society reveal, when considered appropriate, he was also perfectly willing and able to write clearly in layman English.

Most of his findings and conclusions held right up until the 20th century, when they were to be refined and revised where necessary by Albert Einstein himself.

It's interesting to note that in his long and highly detailed letter to the Royal Society (6/2/1672) regarding his theory of light and colours, at note 5. he writes:

'There are therefore two sorts of colors: the one original and simple, the other compounded of these. The original or primary colors are red, yellow, green, blue and a violet-purple, together with orange, indigo and an indefinite variety of intermediate graduations.
6. The same colors in specie with these primary colours may be also produced by composition, For a mixture of yellow and blue makes green; of red and yellow makes orange; of orange and yellowish green makes yellow. And in general if any two colors be mixed which, in the series of those generated by the prism, are not too far distant one from another, they by their mutual alloy compound that color which in the said series appeareth in the mid-way between them. But those which are situated at too great a distance, do not so. Orange and indigo produce not the intermediate green, nor scarlet and green the intermediate yellow.'

Artists generally limit the primary colours to red, blue and yellow. These determine the secondary colours which also accord with the natural principle of polarity, as well as a simple rule of three. Yet in printing for example, majenta, cyan and yellow (and black, which theoretically would be the blended results of all the colour components) are the used primaries. In visual, digital electronics, red, blue and green (instead of yellow) are the primaries.

Newton's note 7. expresses his wonder and admiration of the composition of 'whiteness' compounded by the primary colours.
This reminds me of an endearing demonstration during a colour theory class when the college head, intent on proving that the spectrum of colours produces white, tried to spin a spectrum disk before us, only to see it fly off above our heads around the room, to our great delight. Yet, to his credit before the disk launched itself, it was just beginning to produce the desired effect of a sort of off-white.

From A Letter of Mr. Isaac Newton, Professor of the Mathematics in the University of Cambridge, Containing His New Theory about Light and Colors here's his notes 7 to 10, then finally 13.

'7. But the most surprising and wonderful composition was that of whiteness. There is no one sort of rays which alone can exhibit this. 'Tis ever compounded, and to its composition are requisite all the aforesaid primary colors, mixed in due proportion. I have often with admiration beheld that, all the colors of the prism being made to converge and thereby to be again mixed as they were in the light before it was incident upon the prism, reproduced light, entirely and perfectly white, and not at all sensibly differing from direct light of the sun, unless when the glasses I used were not sufficiently clear; for then they would a little incline it to their color.
8. Hence therefore it comes to pass that whiteness is the usual color of light, for light is a confused aggregate of rays endued with all sorts of colors, as they are promiscuously darted from various parts of luminous bodies. And of such a confused aggregate, as I said, is generated whiteness, if there be a due proportion of the ingredients; but if any one predominate, the light must incline to that colour, as it happens in the blue flame of brimstone, the yellow flame of a candle, and various colors of the fixed stars.
9. These things considered, the manner how colors are produced by the prism is evident. For of the rays constituting the incident light, since those which differ in colour proportionally differ in refrangibility, they by their unequal refractions must be severed and dispersed into an oblong form in an orderly succession from the least refracted scarlet to the most refracted violet. And for the same reason it is that objects, when looked upon through a prism, appear coloured. For the difform rays, by their unequal refractions, are made to diverge towards several parts of the retina, and there express the images of things colored, as in the former case they did the sun's image upon the wall. And by this inequality of refractions they become not only colored, but also very confused and indistinct.
10. Why the colors of the rainbow appear in falling drops of rain is also from hence evident. For those drops which refract the rays disposed to appear purple in greatest quantity to the spectator's eye, refract the rays of other sorts so much less as to make them pass beside it;º and such are the drops on the inside of the primary bow and on the outside of the secondary or exterior one. So those drops which refract in greatest plenty the rays apt to appear red toward the spectator's eye, refract those of other sorts so much more as to make them pass beside it; and such are the drops on the exterior part of the primary and interior part of the secondary bow.
13. I might add more instances of this nature, but shall conclude with this general one, that the colors of all natural bodies have no other origin than this, that they are variously qualified to reflect one sort of light in greater plenty than another. And this I have experimented in a dark room by illuminating those bodies with uncompounded light of divers colors. For by that means any body may be made to appear of any colour. They have there no appropriate color, but ever appear of the color of the light cast upon them, but yet with this difference, that they are most brisk and vivid in the light of their own daylight color. Minium¹ appeareth there of any color indifferently with which 'tis illustrated, but yet most luminous in red, and so Bise² appeareth indifferently of any color with which 'tis illustrated, but yet most luminous in blue. And therefore minium reflecteth rays of any color, but most copiously those endued with red; and consequently when illustrated with daylight, that is, with all sorts of rays promiscuously blended, those qualified with red shall abound most in the reflected light, and by their prevalence cause it to appear of that color. And for the same reason bise, reflecting blue most copiously, shall appear blue by the excess of those rays in its reflected light; and the like of other bodies. And that this is the entire and adequate cause of their colors is manifest, because they have no power to change or alter the colors of any sort of rays incident apart, but put on all colors indifferently with which they are enlightened.
These things being so, it can no longer be disputed whether there be colors in the dark, nor whether they be the qualities of the objects we see, no, nor perhaps whether light be a body. For since colors are the qualities of light, having its rays for their entire and immediate subject, how can we think those rays qualities also, unless one quality may be the subject of and sustain another- which in effect is to call it substance. We should not know bodies for substances were it not for their sensible qualities, and the principle of those being now found due to something else, we have as good reason to believe that to be a substance also.³
Besides, who ever thought any quality to be a heterogeneous aggregate, such as light is discovered to be? But to determine more absolutely what light is, after what manner refracted, and by what modes or actions it produceth in our minds the phantasms of colors, is not easy. And I shall not mingle conjecture with certainties.'                         (1672)

°disappear by it
¹ Red lead
² Azurite blue
³ Our senses perceive a body as a substance by its quality. The main quality of a body is its colour, but this is known to be a quality of light and not body.


Intro texts and photo of rainbow © Mirino. (Part of a portrait of Newton. Artist unknown). Souces include The Norton Anthology English Literature. Volume 1. Extracts from Isaac Newton's letter to the Royal Society. With thanks. May, 2012

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