1
Prelude

pre-lude

pr?lju?d

16th century. From French or mediaeval Latin.

1. noun. Preliminary play, before the real performance.

2. noun. An introduction or preface (to a literary work).

The best idea ever

It happened in the year 1666, not far from Nottingham. The plague was gnawing its way across England like a fetid monster, and in London alone it killed 100,000 people, a quarter of the population. Many townsfolk, terrified by the manifest danger of infection, fled to the countryside. A young student from Cambridge returned to his family home in a small village, and one fine summer's day he sat down under a tree in his mother's orchard. While daydreaming, he saw a ripe apple plop into the grass at his feet. He looked up, studied the sky and wondered whether the force that had made the apple fall might perhaps also be responsible for the trajectory of the moon around the earth.1

That was it. The best idea ever.

In a more romantic version of the story, the apple falls on Isaac Newton's head. Although tempting, it would probably be a mistake to believe that version. We don't even know for certain whether his brilliant musings were the result of a falling apple, but several statements to that effect, including those of Newton himself, make it quite plausible.

Ever since Aristotle, people had believed that the laws of nature on earth were fundamentally different from those that regulated the unfathomable movements of the heavenly bodies. Newton taught us that they arose out of the same principle. Objects attract other objects, with a force that can be calculated precisely, using mathematics, based on mass and distance. Before the publication of Newton's most important work, the Principia, a forward leap of such magnitude had never been made in our understanding of the world. Nor has it been equalled since.

Newton's childhood was far from easy. His father died before he was born; his mother then married a man who did not want a stepson and, at the age of three, Isaac was sent to live with his grandmother. He must often have felt lonely. At school, he was bullied. He fantasized about the death of his stepfather, and of his mother. In a fit of rage, he threatened to burn down his stepfather's house. Sometimes he wished he was dead.

Isaac liked drawing circles and other geometrical shapes, and outdoors he made sundials by hammering wooden pegs into walls and into the ground so that he could measure time. Such devices were accurate to a quarter of an hour. He also carved sundials into stone. His stepfather died when he was ten and his mother returned to her old house, along with Isaac and three younger children. Isaac was sent to school in Grantham, a small town 8 kilometres away, where he lived in the local apothecary's attic. He had no friends. At school he learned Latin, Greek, theology and elementary mathematics. Isaac was surely destined to become a farmer like his father, so it would be useful for him to learn some practical arithmetical skills that would enable him to calculate surface areas and the like. The boy went far beyond that, however. He constructed watermills, windmills and a functioning water clock. He hung lanterns on the home-made kites that he flew, to the horror of the neighbours, who suddenly saw bright lights moving across the nocturnal darkness. He consulted the astronomical tables, and in his notebook he compiled a calendar for the coming twenty-eight years.

When Isaac was sixteen, his mother removed him from school. She felt it was time for her son to take up the serious role of man of the house and become a yeoman farmer. Out in the meadows, Isaac became utterly absorbed in making a new watermill, failing to notice that his sheep were trampling the neighbour's barley. He neglected the fencing, allowing his pigs to wander off, and he was fined by the owner of the land they churned up. He argued with his mother and his half-sisters, and eventually his former schoolmaster decided to intervene. With the help of one of Isaac's uncles, a church minister, the teacher managed to persuade Isaac's mother that the boy must be allowed to study. He was exceptionally intelligent, and exceptionally poorly suited to farming life. In 1661, Isaac Newton travelled to Cambridge and reported at the Great Gate of Trinity College.

The scientific revolution that was taking place at the time advanced human knowledge at a pace never seen before in the history of the world, not even in Ancient Greece. Newton was taught about Aristotle, and in the college library he read the works of Galileo, Bacon and Descartes. 'If I have seen further, it is by standing on the shoulders of Giants', he said many years later. He continually made notes, and in his second year at university he used the term 'gravity' for the first time. It was a word that dated back to around 1500, derived from the Latin 'gravitas' and used to refer to the tendency of objects to fall consistently downwards to the lowest point they could reach. Why objects did this, nobody knew. Newton also kept notes on concepts he wanted to understand better: heat and cold, attraction, magnetism, colour, sound, memory and the tides. Might the moon be capable of compressing the earth's atmosphere and thereby causing ebb and flood?

Newton read La géométrie by Descartes and other books about mathematics. He spent night after night outdoors in the cold of December to study the path of a comet. Comets were regarded as omens of impending doom in those years, and in England rumours were taking hold of a new epidemic of plague in Holland. The disease crossed the sea and in London the dying began. Newton wrote a letter to his mother, telling her that the university was closing down and he was coming home.

In his mother's house, he built a bookcase and studied to become a mathematician. He regarded mathematics as a universal symbolic language that could be used to describe the world without the need to resort to anything mystical. In this period, he was alone. He didn't talk to anyone and he didn't realize that the mathematics he was working on was new. Like his contemporaries, he had a sense that he was dusting off existing knowledge available to the Ancient Greeks. He refined his concept of geometry, further developed his calculus and used his insights to gain a better understanding of experiments conducted by Galileo, who, seventy-five years earlier, had experimented by dropping spherical objects of different weights from the top of the Tower of Pisa. He was always thinking about mathematical questions, while at the same time appearing to be doing nothing much at all. He would stare outside, gaze at empty sheets of paper and wait for insight. 'Truth is the offspring of silence and meditation', he said.2

Mathematics helped Newton to improve his grasp of Galileo's experiments, but nobody, not even the Ancient Greeks, had realized that mathematics could serve as an instrument for explaining phenomena in the heavens. Newton understood that the apple in the orchard was one of those phenomena. It wasn't just hanging in a tree; like everything else on earth, it was hurtling through space at enormous speed.

And then the apple fell.

The apple plopped into the grass when Newton was just short of twenty-two years old, and another twenty-two years would pass before he published his Principia. First, he continued to expand his understanding of mathematics and studied other matters. He inserted a needle between his eyeball and eye socket and pressed, curious as to what he would see. The answer turned out to be strange white circles. He stared at the sun as long as he could, without eye protection, to investigate what would happen. The result was that he saw light objects as red, dark as blue, and was then forced to shut himself up in a darkened room for three days to recover his eyesight. He studied light using a prism, and may have been relieved to discover that this did not have any damaging effect on his eyes. At the age of twenty-seven, he became a professor at Cambridge. He wrote about his views on religion. Newton believed in God, but not in the Trinity. Jesus was more than a human being, he said, but not the son of God. It almost cost him his job. In the meantime, he worked. He calculated, wrote, thought, mused. Newton wrote 10 million words in his life (more than a hundred times the number in this book), although only a small proportion of them were published.

In 1684, Newton was visited by an admirer of his, the astronomer Edmond Halley, who had discussed the movements of the planets with Robert Hooke and Christopher Wren. All three had a rough idea of the explanation they were hoping to find, but their calculations never quite added up. Furthermore, disagreement arose. Each believed himself to be the first to have taken an important step, and Halley thought that Hooke in particular was bluffing. Halley decided to ask Newton for his view, and Newton said he had worked it all out long ago. When Halley asked for his proofs, however, Newton was unable to produce them straight away. After several months, he sent Halley the first nine pages. When Halley asked for more, Newton put all his other scientific projects on hold. A full two years passed after Halley's visit before Newton sent him the first volume of his Principia. The second and third volumes followed, the British Royal Society published the Philosophiae naturalis principia mathematica and the world...