Isaac Newton: The man who discovered gravity
A genius with dark secrets
Isaac Newton changed the way we understand the Universe. Revered in his own lifetime, he discovered the laws of gravity and motion and invented calculus. He helped to shape our rational world view.
But Newton’s story is also one of a monstrous ego who believed that he alone was able to understand God’s creation. His private life was far from rational – consumed by petty jealousies, bitter rivalries and a ruthless quest for reputation.
25 December 1642
Not expected to survive the day
Newton was born prematurely on Christmas morning, in Woolsthorpe, Lincolnshire. He was a tiny baby, given little chance of survival.
The country he was born into was chaotic and turbulent. England was being torn apart by civil war. Plague was an ever-present threat. Many believed the end of the world was imminent. But the hamlet of Woolsthorpe was a quiet community, little touched by either war or plague, which respected Puritan values of sobriety, simple worship and hard work.
A lonely boy who hated his stepfather
Newton’s father had died before he was born. When Isaac was three, his mother left him with his grandmother and married a man from a nearby village.
This turbulent start scarred Newton for life. He felt rejected by his family. He hated his stepfather and threatened to burn his house down. At Grantham school, Newton sought solace in books. He was unmoved by literature and poetry but loved mechanics and technology, inventing an elaborate system of sundials which was accurate to the minute. While his mother hoped he would run the family farm, his uncle and his headmaster realised Newton was destined for an intellectual life.
A mathematical mentor
Newton enrolled at Trinity College, Cambridge. Here he found a father figure who set him on the road to important discoveries.
Isaac Barrow, Cambridge's first professor of mathematics, steered Newton away from the standard undergraduate texts and towards the big unsolved mathematical problems of the day, such as calculus - a way of describing how things change. Calculus would later be crucial for explaining the universe in mathematical terms. Newton also hunted out new works by men such as Descartes, who argued that the Universe was governed by mechanical laws.
Newton’s productive plague years
When Cambridge University was closed because of the plague, Newton was forced to return home. This was the most productive period of his life.
Newton was driven by the belief that the path to true knowledge lay in making observations rather than reading books. For example, rather than trust texts on optics, he experimented by sticking a bodkin – a blunt needle – in his eye to see its effect. He laid the groundwork for his theories of calculus and laws of motion that would later make him famous. But, naturally secretive, he kept his ideas to himself.
New ideas lead to a revolutionary new telescope
Newton continued to experiment in his laboratory. This mix of theory and practice led him to many different kinds of discoveries.
His theory of optics made him reconsider the design of the telescope, which up until this point was a large, cumbersome instrument. By using mirrors instead of lenses, Newton was able to create a more powerful instrument, 10 times smaller than traditional telescopes. When the Royal Society heard about Newton’s telescope they were impressed. This gave Newton the courage to tell them what he described as a ‘crucial experiment’ about light and colours.
Taking criticism badly
The Royal Society was an elite group who met to share and critique each other’s work. They encouraged Newton to share his ideas.
But Newton's theories about light did not go down well. Other members of the Royal Society could not reproduce his results – partly because Newton had described his experiment in an obscure manner. Newton did not take the criticism well. When Robert Hooke challenged Newton’s letters on light and colours, he made a lifelong enemy. Newton had an ugly temper and an unshakable conviction that he was right. With his pride dented, he began to withdraw from intellectual life.
A self-imposed exile
Smarting from criticism, Newton isolated himself from other natural philosophers and dedicated himself to radical religious and alchemical work.
With his mother on her deathbed, he returned home to Woolsthorpe and embarked on a period of solitary study. He became absorbed in alchemy, a secretive study of the nature of life and the medieval forerunner of chemistry. Some argue that these ideas, while not scientific in the sense that we understand them now, helped him think radical thoughts that shaped his most important work, including his theories of gravity.
Newton's greatest rivalry begins
When German philosopher Gottfried Leibniz published an important mathematical paper, it was the beginning of a lifelong feud between the two men.
Leibniz, one of Europe’s most prominent philosophers, had set his mind to one of the trickiest problems in mathematics – the way equations could describe the physical world. Like Newton, he created a new theory of calculus. However, Newton claimed he'd done the same work 20 years before and that Leibniz had stolen his ideas. But the secretive Newton hadn't published his work and had to hastily return to his old notes so the world could see his workings .
The Principia Mathematica: A foundation of modern science
Challenged by Robert Hooke to prove his theories about planetary orbits, Newton produced what is considered the foundation for physics as we know it.
The Philosophiae Naturalis Principia Mathematica took Newton two years to write. It was the culmination of more than 20 years of thinking. It outlined his own theory of calculus, the three laws of motion and the first rigorous account of his theory of universal gravitation. Together, this provided a revolutionary new mathematical description of the Universe. The work cemented his reputation and contains much of what he is remembered for today.
Newton enters the world of politics
Having made his name as a natural philosopher, Newton was attracted to a new life as a politician and public figure.
Profoundly religious, Newton could not sit by while James II attempted to re-Catholicise Cambridge University – even if it meant nailing his own religious colours to the mast. He successfully fought James's reforms and got himself elected as a Member of Parliament. However, he made little impact in the Commons and appears on record only to ask for a window to be closed.
Exhaustion and breakdown
In mid-1693, Newton suffered a mental collapse when he suspected that his friends were conspiring against him.
After working five nights in a row, Newton suffered what we might describe as a nervous breakdown. He later apologised to the philosopher John Locke and to the MP Samuel Pepys for having wished them dead, though whether he actually wished this is unclear. Yet Newton's fragile mental health did not dent his public reputation. He was soon offered an important new post.
Newton saves Britain's currency
As warden of the Royal Mint, Newton found a new calling. He attempted to make Britain's currency the most stable in the world.
In the 17th Century, Britain's finances were in crisis. One in every 10 coins was forged, and often the metal in a coin was worth more than the face value of the coin itself. Newton oversaw a huge project to recall the old currency, and issue a more reliable one. Always methodical, Newton kept a database of counterfeiters, and prosecuted them with a puritanical fury. He was appointed Master of the Mint in 1700 and held the post for the rest of his life.
Newton elected president of the Royal Society
As the leading figure in British natural philosophy, Newton had completed his most important work. Now he set about securing his reputation.
Newton was an imposing leader, obsessed by power and reputation. Though he continued to publish his own work, he also worked to make and break the reputations of other men. He tried to write Hooke out of history and began another bitter dispute with astronomer John Flamsteed by publishing Flamsteed's catalogue of stars without his consent. Newton remained an influential figure, surrounded by a new generation of students brought up on his ideas.
Newton re-writes history in his favour
Newton and Leibniz had quarrelled over who invented calculus. Now Newton saw a way to triumph over his intellectual nemesis.
In 1713, the Royal Society formed a committee to decide once and for all who invented calculus. It found that Newton had beaten Leibniz by many years. However, the secret author of the Royal Society report was none other than Newton himself. Leibniz refused to concede defeat, and the feud only ended once both men were dead. Today, it is accepted that both men arrived at the calculus independently.
Newton creates a legend
At the very end of his life, Newton told a story which has become one of the most enduring legends in the history of science.
Dining with fellow Royal Society member William Stukeley, Newton remembered that he had been sitting beneath an apple tree at his family home of Woolsthorpe, and a falling apple had prompted him to think about gravity. The story was also told by other people who knew Newton, including his niece Catherine who cared for him in his later years. However, the myth that Newton was hit on the head by the apple was a later invention.
20th March 1727
Newton died aged 84, and was buried with full honours in Westminster Abbey. As a celebrated natural philosopher, he was a new kind of national hero.
Newton laid the foundations for our scientific age. His laws of motion and theory of gravity underpin much of modern physics and engineering. Yet he had believed he was put on Earth to decode the word of God, by studying both the scriptures and the book of nature. For him, theology and mathematics were part of one project to discover a single system of the world.