Inspirational Thinkers, The Original Apple Man: Sir Isaac Newton

By  

Engr. Shehu Usman Abdullahi

sheikhbeta@yahoo.co.uk

Centuries before Steve Jobs and Stephen Wozniak had made the apple more than just the name of a fruit when the pair developed the Apple Computer, the apple fruit had another association with an even more famous personality: the honour for the earlier association went to Sir Isaac Newton. But such is the towering genius of the great man, that in linking his name to that of an apple – or any other fruit for that matter – the honour is actually being done to the fruit.

Never mind the possibility that the legend of Newton and the falling apple might have been apocryphal but, as with the story of Archimedes’ discovery of the laws of floatation, it is still a compelling and inspiring tale. As the account goes, Newton was sitting in an orchard when an apple fell from one of the trees. Now there is nothing remarkable about this: fruits fall from trees all the time. Before Newton , the tendency of a body to fall toward the earth was regarded as an inherent property of all bodies – a ‘natural’ occurrence needing no further explanation. So whereas most people might ignore the falling apple altogether or, perhaps, eat it; for Newton the fall sparked off meditations of such profound nature that were to change the then conventional views of the universe in a fundamental way

Newton wondered if the force which caused the apple to fall to the earth might be the same one keeping the moon in its orbit around the earth, preventing it from flying off into space. In other words, he reasoned that the centripetal – or circular – acceleration of the moon around its orbit and the downward acceleration of a body on earth might have the same origin. This was a very revolutionary view at the time; for the conventional wisdom then, very much influenced by the teachings of the great Aristotle, was that the rules governing celestial motion, as in the case of the moon, were different from those governing terrestrial motion, as in the case of the apple. Newton , like all great minds, refused to be swayed by mere conventions, not even when they were given respectability through association with a famous personality.

Newton ’s contemplations on the nature of gravity came after several years of academic work in other fields, particularly in investigating the nature of light. He had toiled silently in Cambridge and, during the outbreak of the bubonic plaque, at his family home in rural Woolthorpe, virtually unrecognised by the outside world. For much of these earlier years he did not even come to the notice of his colleagues at the Royal Society of London, then the foremost scientific society in Great Britain if not the whole world.

But these were still early days in the distinguished career of Newton . In his undergraduate years at Cambridge , from 1661 to 1665, the great man allowed his mind a free reign over several subjects, not all of them necessarily within the official academic curriculum. He studied the works of Aristotle, then just coming to vogue in the university. Aristotle’s ideas, for all their wide range, were not very influential in the intellectual development of Newton ; those of the French philosophers René Descartes and Pierre Gassendi approximated more to his own thinking. He also studied the works of the English chemist Robert Boyle as well as that of the philosopher Henry Moore. Newton ’s studies at this time covered the works of men who sometimes espoused ideas contradictory to each other.

Meanwhile, the budding genius was shaping ideas of his own. At first he jotted down what he described as “Certain Philosophical Questions”, in which he enumerated aspects of human knowledge which he felt remained unanswered by the philosophers of the day. He then delved into mathematics where he developed the Binomial Theorem and the field that was to become known as Calculus, though Newton called it by the rather quaint name of Fluxions.

Newton confined all these early efforts to his notebooks. Thus when he graduated from Cambridge in 1665 he was still unknown to all but his immediate academic circle. In the same year, the plague broke out and Cambridge was closed down for two years. At home in Woolthorpe Newton continued with his contemplations which included the episode in the apple orchard leading to initial work on gravitation. Other areas included further development of calculus and works in optics – the study of the nature of light.

It was during this period that Newton carried out his famous experiment in which he allowed a ray of sunlight to pass into a darkened room through a slit in the curtain and placed a glass prism on its path. Newton then observed that when he let the emerging rays fall on a screen, a coloured band in the familiar pattern of the rainbow – red, orange, yellow, green, blue, and violet – appeared on it. This is the phenomenon that would come to be known to all physics students as refraction – the process by which white light is separated into its constituent parts in proportion to the respective wavelengths of those parts. The refracted light created a spectrum displaying the degrees to which the constituent colours had been bent: with red rays, which possess the longest wavelengths, being bent the least and violet rays, having the shortest wavelengths, bent the most.

In order to further confirm that the different spectral colours actually came from the white light and were not somehow produced by the glass prism, Newton placed a second prism, oriented in reverse to the first, in front of the refracted coloured rays and obtained a single point of white light, in effect recombining the rays to form the original white light. When he placed the prism in front of only one coloured ray, instead of all of them, only the coloured ray appeared, sometimes contracted, and at other times broadened, depending on the orientation of the prism, but always remaining that single coloured ray.

Furthermore, Newton showed that in any case refraction occurred in other transparent media apart from glass – water, for example. He proved that the rainbow we all see at one time or another was but a result of the refraction of sunlight by droplets of water in the moist sky and not – as some superstitious ancients used to dread – a manifestation of heavenly displeasure or precursor of poor rainfall.

Newton returned to Cambridge at the end of the plaque, in 1667, still unknown to the outside world; but this was to quickly change. Two years later, in 1669, his mathematics teacher, Isaac Barrow, decided to resign his professorship in Cambridge and recommended Newton as his replacement. Thus, at the early age of 27 Newton become Lucasian professor of mathematics (after Henry Lucas, who founded the Chair) at the illustrious university.

Even the Royal Society cannot continue to ignore an individual of this accomplishment, especially one brimming with original ideas as Newton . It was not long before the Society heard about the latest device created by the great man, the reflecting telescope, and requested to see it.  The Society was impressed with what it saw and, in 1671, elected Newton a member.  

The reflecting telescope was an indirect result of Newton ’s works with prisms, and a departure from the telescopes in existence before then, which were all of the refracting type. The earlier telescopes all suffered from the drawback resulting from distortions caused by the dispersion of the light coming from the heavenly bodies by the prisms and lenses within the telescopes, which then cast coloured rims around the images of the bodies, distorting details. Newton believed at the time that this phenomenon, known as ‘chromatic aberration’, imposed a limit on the utility of refracting telescopes; making them larger simply amplified the problem. So he decided to construct a new telescope which reflected, rather than refracted, light.

Emboldened by the enthusiastic reception his telescope elicited from the members of the Royal Society, Newton volunteered to let them have a look at his other works in optics, only to land smack into his first, though by no means last, intellectual controversy. For the secretary of the Royal Society at this very time was a certain Robert Hooke, known to most science students of today as the man who developed the law of extension of elastic materials subjected to a force, otherwise known as Hooke’s law.

Clearly, Robert Hooke was no intellectual midget, but was nevertheless something of an I-did-it-before-you bully. In the words of Isaac Asimov, Hooke “was on the one hand a most ingenious and capable experimenter in almost every field of science, and on the other a nasty, argumentative individual, anti-social, miserly, and quarrelsome.  Since he investigated in a wide variety of fields, he frequently claimed (with some justice) that he had anticipated the more thorough and perfected ideas of others.”

To cut matters short, Hooke accused Newton of stealing his ideas in optics, whereupon Newton overreacted and revealed an uncomplimentary, rather childish, side to his character. Peer review and criticisms, sometimes viscious criticisms, had been a part of scientific discourse from time immemorial, but Newton would have none of that. At the slightest sign of such attacks, the great man flew into a rage and withdrew into a shell, often threatening to abandon further publication of his works altogether. As Bertrand Russell observed when speaking of Newton , “If he had encountered the sort of opposition with which Galileo had to contend, it is probable that he would never have published a line.”

At any rate, after his run-in with Hooke, and unable to continue with the give and take of the intellectual discussion his papers provoked, he more or less temporarily broke contact with the Royal Society and even threatened to resign from it. Not until a few years later, in 1675, did he submit a second paper dealing with the colour phenomenon in thin films, otherwise known as diffraction.  An accompanying piece to this paper also prompted further rounds of controversy with the contentious Hooke.

Many great scientists tended to belong to one of two basic breeds. Some, like Thomas Alva Edison, were better at the practical application of their talents; others were stronger on theoretical exposition: the great Albert Einstein was the most notable personality in this group. Newton , however, belonged to the small exclusive club of scientists who can lay claim to both sides. He was both a skillful experimenter as well as an excellent theoretical physicist. His works in light, as in gravitation, demonstrated this fact.

During the time of Newton and much later, the great debate about the nature of light was whether it existed in the form of particles (the particle or corpuscular theory), or in a wave form. Newton belonged to supporters of the particle theory, his strongest evidence being the fact that light casts sharp shadows, and travels in a straight line unable to bend around corners, unlike sound which, because it is propagated in a wave form, is able to.

However, a number of difficulties defied explanations using the particle nature of light. Robert Hooke, the Dutch physicist Christiaan Huygens and, a little later, the gifted English physicist Thomas Young, were notable wave-form advocates who pointed out such complications. Young in particular advanced strong arguments for light being a wave form through an experiment in which light was shone through a tiny opening whereupon separate bands of light appeared, instead of the sharp edges of the opening which should have appeared according to the particle theory. As mentioned earlier, these diffraction bands had been noted by Newton himself, but he could not explain them by the particle theory of light. For over a century the debate continued, until Albert Eistein came along to show that both sides could be right depending on the circumstances, by espousing the dual nature of light.

After his works in optics, Newton appeared to enter into a period of intellectual seclusion caused partly by his fits of tantrums with the Royal Society and other groups that challenged his theories. He was in fact to suffer a temporary mental breakdown which further exacerbated his isolation. During this period Newton slipped into mysticism and the fruitless field of Alchemy, trying to change base metals into gold or silver. This was however a temporary phase in the life of the great man: he was to bounce back with perhaps his greatest contribution to mankind – the theory of universal gravitation.

 -- to be continued--

Engr. S. U. Abdullahi

NNDC Qtrs., Kundila

Kano