Isaac Newton: The Last Sorcerer. Michael White

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      There is no clear point at which the Dark Ages ended in Europe. Learning in some form had been kept alive in the monasteries, but the interest of the Christian fathers had lain in mysticism and religious relevance rather than practical or theoretical science. The Arabs, who had made great strides in the understanding of alchemy, mathematics and astronomy throughout the period, maintained an interest in pure science, and as this knowledge filtered gradually into Europe the shadow of ignorance lifted. But it was a slow process, taking three or four hundred years.

      Sometime between 1200 and 1225, Aristotle’s works, which had been saved in part by the Arabs and amalgamated with their own ideas, were rediscovered by European intellectuals and translated into Latin. From this point on, Aristotle’s science returned to favour and took over from Platonic mysticism, gradually fusing with Christian theology.

      Although this development may be viewed as an improvement upon the Dark Age mistrust of science and the Stoics’ preoccupation with spirituality, it created a new obsession – a marriage of Aristotelian natural philosophy with Christian dogma. This meant that any attack upon Aristotle’s science was also seen as an attack upon Christianity. Together, the two doctrines formed a powerful alliance and created a world-view that was taught by rote almost unchallenged in every university in Europe for almost half a millennium, from the thirteenth to the seventeenth century.

      These twinned beliefs produced a self-contained picture of the universe: God created the world as described in the Scriptures and guided all actions. All movement was not only set in motion by God but was supervised by divine power. The Church’s doctrine of divine omnipotence thus dovetailed perfectly with Aristotle’s belief in the Unmoved Mover – that no movement was possible unless initiated by an unseen hand. All matter consisted of the four elements and was not divisible into atoms as Democritus had proposed. To Aristotle, every material object was an individual complete entity, created by God and composed of a particular combination of the four elements. Each object possessed certain distinct and observable qualities, such as heaviness, colour, smell, coolness. These were seen as solely intrinsic aspects or properties of the object, and their observed nature had nothing to do with the perception of the observer.

      To the thirteenth-century mind, the notion that properties of an object such as smell, taste or texture were partly open to interpretation in the mind of the observer would have been totally alien. Every property of an object was intrinsic and the same for all observers. Furthermore, because Aristotle had rejected atomism, the concept that matter was composed of tiny, indivisible elements would have been equally foreign to most people of the time. And, because Aristotelian ideas were now bound up inextricably with religion, any philosopher who openly challenged any aspect of accepted scientific ideology put his life in danger.

      Yet, despite the severe limitations this placed upon the development of scientific inquiry, the Middle Ages did produce a collection of notable and original thinkers who contributed to a gradual reawakening of rationality. Together, these men led the way to the Renaissance and the full flowering of innovative science that followed.

      Still wrapped up in the need to marry natural philosophy with theology, the thinkers of this period – who became known as the Scholastics, the most famous of whom were St Thomas Aquinas and Albertus Magnus – stuck to the traditional Aristotelian line, shunning experiment. However, they did champion the search for truth outside the limited realm of pure theology. Although they maintained a firm belief that man was the central object of Creation and that the universe was designed for man by God, they had progressed to the idea that the study of Nature and the physical world could lead to greater theological enlightenment. It was not until the deaths of Aquinas and Albertus Magnus (towards the end of the thirteenth century, some seventy-five years after Aristotle had been reintroduced into Europe) that the work of the great Oxford scholar Roger Bacon began to erode the restrictions of Scholasticism.

      In some ways Bacon was a man born ahead of his time. Although he subscribed to many traditional beliefs of the Scholastics, he was the first to see the usefulness of experiment and he composed three far-sighted tracts – Opus Majus, Opus Minor and Opus Tertium – which outline his philosophy and his experimental techniques in a range of disciplines. This effort established Bacon’s reputation for posterity, but did little for him during his lifetime. Viewing his work as anti-Establishment and its anti-Aristotelian elements as subversive, Jerome of Ascoli, General of the Franciscans (later Pope Nicholas IV), imprisoned him for life as a heretic.

      The scientific renaissance that followed Bacon’s time marks a change in philosophical beliefs every bit as significant as that in the arts. Men such as Leonardo da Vinci, who approached science from a practical standpoint, foreshadowed many of the ideas of Galileo, Kepler and Newton, but did not write up their discoveries in any coherent form. The best we have is Leonardo’s collection of notebooks, which indicate his studies and philosophies. In one sense, Leonardo was all experiment and represented the opposite extreme to the Greeks.

      Leonardo held an opposing view of motion to Aristotle. Aristotle claimed that nothing moved unless it was made to do so by God, the Unmoved Mover. Leonardo suggests the exact opposite, writing in his notebook, ‘Nothing perceptible by the senses is able to move itself … every body has a weight in the direction of the movement.’⁴ In other words, matter has an innate tendency to move in a certain direction unless stopped. This anticipates the notion of inertia first postulated by Galileo some half-century later and eventually formalised by Newton.

      Galileo, who was born in 1564 (about forty years after Leonardo’s death), is regarded by historians of science as the greatest thinker in the realm of motion and matter up to Newton’s time. It is generally agreed that his practical demonstrations paved the way for Newton’s own blend of experimental verification and mathematical integrity.

      Galileo’s work in this area was revolutionary because he was the first to devise repeatable experiments that showed that Aristotle’s ideas were quite wrong. He is probably most famous for his use of the telescope, which destroyed the traditional ideas of how the solar system is constructed (see Chapter 4), but equally important for the progress of science was his work in what became known as the science of dynamics.

      Aristotle held that bodies were either intrinsically light or heavy and they fell at different velocities because of their innate tendency to seek their natural places. In 1590 the Flemish philosopher Simon Stevin had shown that light and heavy objects falling through a vacuum reach the ground simultaneously. Galileo repeated this experiment the following year (although probably not from the Leaning Tower of Pisa as tradition had it) using a cannonball and a musket-ball and showed that the two fall at equal speed if the resistance of air is ignored.

      More importantly, Galileo suspected from this experiment that a falling body moves with a speed proportional to the time it has been falling. But, because the balls fall too quickly for the eye to measure their actual speed, he could not formulate a mathematical relationship between the speed of descent and the time it took. In order to find this relationship, he needed to conduct an experiment in which the speed of descent could be measured.

      He quickly established that, ignoring friction, an object rolling down an inclined plane acquires the same speed as it would if it was falling vertically through the same distance. This enabled him to construct a series of experiments in which he let balls roll along inclined planes and measured the time of their journey and their speeds. This confirmed that the speed of a falling object does indeed increase with the time of the fall.

      In a variation on this experiment, he allowed a ball to roll down an inclined plane and roll up another. In a further test, he allowed the ball to travel on beyond the slope along СКАЧАТЬ