Sir Isaac Newton (1643–1727) stands as one of the most influential figures in scientific history, whose discoveries transformed our understanding of the physical world. Known primarily for his laws of motion and universal gravitation, Newton’s work laid the groundwork for classical mechanics, significantly advanced mathematics, and changed the way humanity perceives the natural universe. This article delves into Newton’s life, his groundbreaking contributions, and the legacy that endures centuries later.

At the age three, his life changed again, when his mother remarried and moved away to live with her new husband, Barnabas Smith, a wealthy clergyman. Newton was left under the care of his maternal grandmother, Margery Ayscough, which profoundly affected him.

Historians suggest that the experience of being effectively abandoned by his mother may have contributed to his later introspective, sometimes reclusive nature, and his intense drive for achievement. Newton’s complex and often solitary personality might have had roots in this early separation and sense of displacement.

Education Beginnings:

Newton’s formal education began at local village schools in Skillington and Stoke. However, in 1655, at around age 12, he moved to the King’s School in Grantham, a prestigious grammar school about seven miles from Woolsthorpe. There, Newton initially lived with the Clarke family, who ran an apothecary’s shop. Living with them is thought to have sparked his early interest in chemistry and alchemy, fields that would captivate him throughout his life.

While at King’s School, Newton showed an interest in mechanics, building various models of machines, including a windmill and a water clock. According to biographers, Newton was relatively introverted, but he displayed an impressive aptitude for constructing mechanical models, as well as for drawing and poetry, which were unusual for someone in his environment. His work in mechanics would foreshadow his later interests in physics and mathematics.

Return to Farming:

Unfortunately, in 1659, Newton’s education was interrupted, because his mother returned to Woolsthorpe due to the death of her second husband. She expected her 17-year-old son to manage the family’s estate and farms, a common duty for the eldest male in rural England. But Newton had neither the skills nor the interest in farming.

According to the book “Never at Rest: A Biography of Isaac Newton” by Richard S. Westfall, Newton’s uncle, William Ayscough, a Cambridge graduate, recognized his potential and persuaded his mother to allow him to continue his studies. Hannah agreed, and in 1661, Newton returned to King’s School, where he prepared to enter the University of Cambridge.

Admission to Cambridge:

According to the book “The Life of Isaac Newton” by David Brewster, in 1661, at age 18, Newton entered Trinity College, Cambridge, as a subsizar—a student who worked as a servant for wealthier students in exchange for reduced fees. He was recommended to the university by his uncle Willian Ayscough, who also had studied at Cambridge. At Cambridge, Newton started as a subsizar until he was awarded a scholarship in 1664, which covered his university costs for four more years, until he completed his MA. At Cambridge, he studied under the formal curriculum, which was largely based on Aristotle’s works and traditional scholastic teachings. However, Newton’s intellectual curiosity soon drove him beyond the standard curriculum.

While at Cambridge, he began studying the works of leading contemporary scientists and philosophers, including René Descartes, Galileo Galilei, Johannes Kepler, and Thomas Hobbes. These thinkers challenged the Aristotelian view of the cosmos, which still dominated academic teachings at the time. Newton was especially influenced by the work of Descartes, whose mathematical and mechanical approach to natural philosophy laid the groundwork for Newton’s own thinking. He set down in his notebook a series of “Quaestiones” (Quaestiones Quaedam Philosophicae is the name given to a set of notes that Isaac Newton kept for himself during his early years in Cambridge) about the mechanical philosophy as he found it.

In 1664, Newton became a scholar at Trinity, which exempted him from certain fees and provided a stipend. He then took up the study of mathematics, reading texts by mathematicians like Euclid, Apollonius, and John Wallis. Newton’s interest in mathematics deepened when he encountered the work of contemporary mathematician Isaac Barrow, who would become his mentor and later be instrumental in Newton’s academic success. Through Barrow’s teachings, Newton was introduced to geometry, optics, and a burgeoning mathematical field that would later become calculus.

The “Annus Mirabilis” – Years of Solitude and Discovery:

In 1665, Cambridge temporarily closed due to the Great Plague sweeping across England. Newton returned to Woolsthorpe for what would become one of the most productive periods of his life, often referred to as his “annus mirabilis,” or “year of wonders.” During this time, from 1665 to 1666, Newton, in near-isolation, conducted groundbreaking research that would shape the future of science.

During his time at Woolsthorpe, Newton formulated the early foundations of calculus, made significant observations about the nature of light and colour, and began formulating his theory of universal gravitation. These discoveries marked a turning point in science and laid the groundwork for his future accomplishments.

Returning Again to Cambridge And the road to Recognition:

When Newton returned to Cambridge in 1667, his discoveries and theories remained largely unpublished, but his reputation grew among his colleagues. In 1669, at the recommendation of his mentor Isaac Barrow, Newton succeeded Barrow as the Lucasian Professor of Mathematics at Trinity College. This prestigious position gave Newton both the freedom and the platform to further pursue his research, culminating in his monumental work, Philosophiæ Naturalis Principia Mathematica, published in 1687.

Contribution to Science:

The title Lucasian Professor of Mathematics at Cambridge comes with the responsibility to instruct geography. In 1672 and again in 1681, Newton published revised and corrected editions of Geographia Generalis, a geography text originally published in 1650 by Bernhardus Varenius, who had passed away before Newton’s involvement. Varenius had aimed to establish a theoretical basis for geography that linked scientific principles with classical concepts, viewing the field as a blend of science and mathematics applied to quantifying Earth’s features. While it remains uncertain whether Newton ever lectured directly on geography, the 1733 English translation by Dugdale and Shaw includes a preface indicating that Newton’s editions were intended as study material for students, possibly in conjunction with lectures on the subject. Scholars note that Geographia Generalis—with Newton’s revisions—has come to represent a shift from classical to modern approaches in geography, with Newton’s contributions thought to be a significant factor in its lasting influence (Westfall, Never at Rest; Dugdale and Shaw, 1733 translation of Geographia Generalis). 

In 1672, Newton was elected as Fellow of the Royal Society.

The Invention of Calculus:

One of Newton’s most profound contributions to mathematics is the invention of calculus, a field essential to modern mathematics, physics, and engineering. During his years in isolation, Newtons develop a new form of mathematics that allowed for the calculation of rates of change and the area under curves, concepts that were challenging to address with existing mathematics.

In June 1669, Isaac Barrow sent Newton’s work “De analysi per aequationer numero terminoru infinitas” to John Collins, and it was identified by Barrow in a letter to Collins that August as the work “of an extraordinary genius and proficiency in these things”.

Newton’s invention of calculus (which he referred to as “the method of fluxions”) allowed him to solve complex problems related to motion and change. Despite being a monumental achievement, it sparked controversy when German mathematician Gottfried Wilhelm Leibniz independently developed his form of calculus around the same time. The Newton-Leibniz controversy over who invented calculus first led to a bitter dispute between their followers and cast a shadow over the latter part of Newton’s life. According to the book “The World of Mathematics” by Newman, James Roy (1956), it is established that Newton came to develop the calculus much earlier than Leibniz. Nonetheless, the importance of calculus in scientific and technological advancements is undisputed.

Newton feared controversy and criticism, that is why he had been reluctant to publish his calculus. Newton was close to the Swiss mathematician Nicolas Fatio de Duillier, who began a revision of Newton’s Principia in 1691 while also corresponding with Leibniz. However, their friendship soured in 1693, and the project was abandoned. By 1699, some Royal Society members accused Leibniz of plagiarizing calculus. Tensions peaked in 1711 when the Royal Society, with a study partly written by Newton himself, declared Newton as the true inventor of calculus and labelled Leibniz a fraud. This marked the start of a fierce dispute that affected both men until Leibniz’s death in 1716.

Newton’s work in Principia Mathematica is deeply rooted in calculus, particularly through his geometric approach using the concept of limiting values involving ratios of quantities that approach zero. In the Principia, he demonstrated this approach under the term “the method of first and last ratios.” Newton explained that he structured his expositions in this way to achieve similar results to the “method of indivisibles,” a technique employed by earlier mathematicians to work with infinitely small quantities.

Because of this approach, Principia has been described by modern scholars as “dense with the theory and application of infinitesimal calculus,” and in Newton’s own era, it was recognized as predominantly based on this form of calculus. His use of infinitesimal methods—those involving “one or more orders of the infinitesimally small”—is also evident in his 1684 work De Motu Corporum in Gyrum (On the Motion of Bodies in Orbit) and in his various papers on motion developed over the two decades leading up to 1684.

Newton is credited with the generalized binomial theorem for any exponent and made key discoveries including Newton’s identities, Newton’s method, and classification of cubic curves. He advanced finite differences, introduced fractional indices, and applied coordinate geometry to solve Diophantine equations. Newton also approximated partial sums of the harmonic series with logarithms and confidently used and reversed power series, influenced by Simon Stevin’s work on decimals.

Optics and the Nature of Light:

Newton’s interest in optics led to revolutionary discoveries about the nature of light and color. In 1666, through a series of experiments, Newton demonstrated that white light is composed of different colours, which he could separate with a prism into a spectrum. This finding contradicted the prevailing belief that colour was a property of objects rather than of light itself.

In 1704, Newton published Opticks, a comprehensive book detailing his experiments and theories on light and colour. He also developed a reflecting telescope, known as the Newtonian telescope, which utilized mirrors rather than lenses, improving image quality by reducing chromatic aberration. His telescope design remains widely used to this day, particularly in astronomical research.

The Laws of Motion and Universal Gravitation:

Newton’s most celebrated work is his development of the three laws of motion and the law of universal gravitation, presented in his landmark book, Philosophiæ Naturalis Principia Mathematica (often simply called the Principia), published in 1687. This monumental work laid the foundations of classical mechanics and transformed our understanding of motion and force.

1. First Law (Inertia): An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
2. Second Law (F=ma): The rate of change of momentum of an object is directly proportional to the applied force, leading to the famous equation F=ma, where F is force, m is mass, and a is acceleration.
3. Third Law (Action and Reaction): For every action, there is an equal and opposite reaction.

Newton’s law of universal gravitation stated that every particle of matter in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. This insight not only explained phenomena such as the falling apple but also accounted for the motion of celestial bodies, like the planets orbiting the Sun, revolutionizing astronomy and physics.

The Principia remains one of the most important scientific works in history, effectively inaugurating the age of classical mechanics. Newton’s theories of motion and gravity held sway in the scientific community until the advent of Albert Einstein’s theory of relativity in the early 20th century.

Newton himself frequently recounted how observing an apple fall from a tree, served as the inspiration for his theory of gravity. The story of Isaac Newton’s inspiration for his theory of gravitation, sparked by watching an apple fall from a tree, was popularized by his niece, Catherine Barton, who shared it with Voltaire (French Enlightenment writer). Voltaire later included the anecdote in his Essay on Epic Poetry (1727), noting that Newton conceived his idea of gravity while observing an apple fall in his garden.

While some argue the apple story is a myth and that Newton’s theory of gravity wasn’t conceived in a single moment, his acquaintances, including William Stukeley, confirm the incident. In Memoirs of Sir Isaac Newton’s Life, Stukeley recorded a conversation from 15 April 1726, where Newton recounted observing an apple fall, though there’s no evidence it hit his head.

Religious View:

Sir Isaac Newton was deeply religious, viewing his scientific work as a way to understand God’s creation, though his beliefs diverged from mainstream Christianity. Newton rejected the doctrine of the Trinity, a stance that classified him as a Unitarian and marked him as a heretic by the standards of the Anglican Church. His religious writings, which were extensive and included studies of biblical texts and prophecies, reveal his conviction that the Bible held hidden knowledge about the natural world and human history. Newton believed that careful study of Scripture, in combination with scientific inquiry, could bring humanity closer to divine truth. He wrote more on theology than on physics or mathematics, including his attempts to predict the end times, a reflection of his lifelong interest in prophecy. These beliefs remained largely private during his life due to potential backlash, but they are documented in his writings, such as those published by the Newton Project, which offers access to his theological manuscripts and notes preserved by the University of Cambridge and other institutions

Alchemy:

Sir Isaac Newton’s interest in alchemy was extensive and long-standing, forming a significant part of his intellectual pursuits outside physics and mathematics. Newton conducted hundreds of alchemical experiments and filled numerous notebooks with alchemical symbols, processes, and theories. He was especially fascinated by the idea that base metals could be transformed into gold and that alchemy might reveal hidden aspects of nature, potentially leading to a deeper understanding of matter and the universe. Alchemy was not viewed as a pseudoscience in Newton’s time but rather as an advanced form of natural philosophy, blending chemistry, mysticism, and proto-scientific inquiry. His alchemical studies were largely secretive and remained unpublished, as he feared public scrutiny and potential accusations of heresy. Today, many of Newton’s alchemical manuscripts are accessible through initiatives like The Newton Project, revealing how seriously he took these pursuits and the influence they may have had on his work in chemistry and physics.

Knighthood:

In April 1705, Queen Anne knighted Isaac Newton at Trinity College, Cambridge, likely for political reasons related to the upcoming parliamentary election rather than for his scientific achievements or his role as Master of the Mint. Newton became the second scientist to be knighted, following Francis Bacon.

Royal Mint:

In 1696, during the period of King William III, Isaac Newton moved to London to take the post of warden of the Royal Mint. It was said that he got this position by the favouritism of Charles Montagu, 1^st Earl of Halifax, then Chancellor of the Exchequer.

Newton oversaw England’s major recoining effort, clashed with Lord Lucas, the Tower’s Governor, and appointed Edmond Halley as deputy comptroller of the temporary Chester branch. After Thomas Neale’s death in 1699, Newton became the renowned Master of the Mint, a role he held for the final 30 years of his life. Though originally a sinecure, he took the position seriously, resigning from Cambridge in 1701 to focus on reforming currency and prosecuting clippers and counterfeiters.

As Warden and later Master of the Royal Mint, Newton estimated that 20% of the coins collected during the Great Recoinage of 1696 were fake. Counterfeiting was considered high treason and carried a severe punishment, but convictions were hard to secure. Despite these challenges, Newton was highly effective at prosecuting counterfeiters.

On 21 September 1717, Newton wrote a report to the Treasury, leading to a royal order on 22 December that set the value of gold guineas at 21 silver shillings. This unintentionally caused a silver shortage, as silver was used for imports while exports were paid in gold, pushing Britain toward a gold standard. It’s debated whether this was Newton’s intention, and some think he saw his Mint work as linked to his alchemical interests. Newton also invested in the South Sea Company, losing about £20,000 when it collapsed around 1720.

Death:

Isaac Newton died in his sleep on 20 March 1727 and was buried in Westminster Abbey, the first scientist to be interred there. His funeral was attended by nobles, scientists, and philosophers, and Voltaire may have been present. A bachelor, he left his estate to relatives and died without a will. His papers were passed to John Conduitt and Catherine Barton. After his death, a plaster death mask was made, which was later used by sculptor John Michael Rysbrack to create a statue. The mask is now held by the Royal Society, which scanned it in 2012. Newton’s hair was found to contain mercury, likely from his alchemical work, and mercury poisoning may explain his eccentric behavior in later life.