## Table of Contents

## Who Was Isaac Newton?

Sir Isaac Newton (1643–1727) was a preeminent physicist and mathematician whose groundbreaking work laid the foundations for modern physics. He is renowned for formulating the laws of motion and universal gravitation, pivotal contributions that revolutionized the scientific understanding of the natural world.

Newton’s seminal work, *Philosophiæ Naturalis Principia Mathematica* (Mathematical Principles of Natural Philosophy), published in 1687, is widely regarded as one of the most influential books in the history of science. This landmark publication not only cemented his status as a leading figure in the 17th-century Scientific Revolution but also established the framework for classical mechanics.

In recognition of his monumental contributions to science, Isaac Newton was knighted by Queen Anne of England in 1705, thereby becoming Sir Isaac Newton. His legacy endures as a cornerstone of scientific thought and inquiry.

## Early Life and Family

Isaac Newton was born on January 4, 1643, in Woolsthorpe, Lincolnshire, England. Under the Julian calendar then in use, his birthdate is occasionally recorded as December 25, 1642.

Newton was the only son of a prosperous local farmer, also named Isaac Newton, who passed away three months before his birth. Born prematurely and frail, Newton’s survival was initially considered unlikely.

At the age of three, Newton’s mother, Hannah Ayscough Newton, remarried Barnabas Smith, a well-to-do minister. Following her remarriage, Hannah moved with her new husband, leaving young Newton in the care of his maternal grandmother.

This early separation had a profound effect on Newton, contributing to a deep-seated sense of insecurity. This insecurity would later manifest in his intense and often obsessive defense of his published work.

At twelve years old, Newton was reunited with his mother following the death of her second husband. She returned with her three young children from the second marriage, reestablishing the family unit.

## Isaac Newton’s Education

Isaac Newton began his formal education at King’s School in Grantham, a town in Lincolnshire. During this period, he resided with a local apothecary, where he was first introduced to the captivating realm of chemistry. At the age of 12, Newton’s education was interrupted when his mother withdrew him from school with the intention of training him as a farmer. However, Newton’s lack of enthusiasm for farming soon became evident, leading to his return to King’s School to complete his basic education.

Recognizing Newton’s exceptional intellectual potential, his uncle—an alumnus of Trinity College, University of Cambridge—convinced Newton’s mother to allow him to pursue higher education. In 1661, Newton enrolled at the University of Cambridge. His early years at the university involved a work-study arrangement, where he managed responsibilities such as waiting on tables and maintaining the rooms of wealthier students.

## The Scientific Revolution and Newton’s Early Career

When Isaac Newton commenced his studies at Cambridge, the 17th century’s Scientific Revolution was already profoundly transforming European intellectual life. The heliocentric model of the universe, initially proposed by Nicolaus Copernicus and further developed by Johannes Kepler and Galileo Galilei, had gained substantial acceptance in academic circles across Europe.

During this period, philosopher René Descartes was pioneering a new perspective of nature as a complex, impersonal machine. However, Cambridge, like many European universities of the time, remained deeply entrenched in Aristotelian philosophy, which adhered to a geocentric view of the universe and approached nature in qualitative rather than quantitative terms.

In his initial three years at Cambridge, Newton followed the standard curriculum but devoted much of his spare time to studying the modern scientific advancements of the era. Although his academic performance during this period was mediocre, this was a result of his intense engagement with contemporary scientific literature alongside his formal studies.

During this time, Newton maintained a second set of notes titled “Quaestiones Quaedam Philosophicae” (“Certain Philosophical Questions”). These notes reveal that Newton had begun to formulate a new conceptual framework for understanding nature, which would later become foundational to the Scientific Revolution. Despite graduating without honors, Newton’s academic work earned him recognition as a scholar and secured him four years of financial support for further study.

In 1665, the bubonic plague that had been sweeping across Europe reached Cambridge, prompting the university’s closure. Newton’s studies were interrupted for two years, but upon his return in 1667, he was elected a minor fellow at Trinity College, despite not yet being considered a distinguished scholar.

Newton’s fortunes began to change in the ensuing years. By 1669, before he was 27, he had earned his Master of Arts degree. During this time, he encountered Nicholas Mercator’s work on methods for dealing with infinite series, which inspired him to write his own treatise, “De Analysi,” detailing his broader results. Although Newton did not initially attribute his work to himself, the manuscript was shared with his friend and mentor, Isaac Barrow.

In June 1669, Barrow presented Newton’s uncredited manuscript to the British mathematician John Collins. By August 1669, Barrow had identified Newton as the author to Collins, describing him as “very young… but of an extraordinary genius and proficiency in these things.” This recognition marked Newton’s initial entry into the broader mathematical community. Shortly thereafter, Barrow resigned his position as Lucasian Professor at Cambridge, and Newton was appointed to the chair, signifying a pivotal moment in his academic career.

## Isaac Newton’s Contributions to Science

Isaac Newton’s groundbreaking contributions span optics, motion, and mathematics. In the field of optics, Newton proposed that white light is a composite of all colors in the spectrum and advanced the particle theory of light.

His seminal work, Philosophiæ Naturalis Principia Mathematica (commonly known as Principia), elucidates fundamental principles of physics, including the laws of motion and the theory of gravity. While it does not address the concept of energy, the Principia remains a cornerstone in the understanding of classical mechanics. Additionally, alongside mathematician Gottfried Wilhelm von Leibniz, Newton is credited with the development of calculus, a pivotal mathematical framework that has profoundly influenced subsequent scientific and mathematical advances.

## Isaac Newton Inventions

Isaac Newton’s early achievements in scientific innovation were marked by his creation of the reflecting telescope in 1668. As a professor at Cambridge University, Newton was tasked with delivering an annual series of lectures and chose to focus initially on the subject of optics. He employed his reflecting telescope to conduct detailed studies of optics, which supported and validated his theories regarding light and color.

In 1671, the Royal Society requested a demonstration of his reflecting telescope, an event that significantly heightened interest in Newton’s work. This encouragement led him to publish his findings on light, optics, and color in 1672. These notes were subsequently compiled and released as part of Newton’s seminal work, Opticks: Or, A Treatise of the Reflections, Refractions, Inflections, and Colours of Light.

## The Apple Myth

Between 1665 and 1667, Sir Isaac Newton returned to his family home from Trinity College to focus on private study due to the closure of the college in response to the Great Plague. During this period, a popular legend suggests that Newton’s groundbreaking insight into gravity was inspired by an apple falling from a tree and hitting him on the head.

This anecdote, though widely circulated, lacks historical evidence. While it is true that Newton observed an apple falling, there is no concrete proof that the fruit struck him. His observation led him to ponder why apples fall straight down rather than at an angle, prompting his exploration into the nature of gravity.

During this 18-month period away from university, Newton made significant strides in his scientific work. He developed the fundamental concepts of infinitesimal calculus, laid the groundwork for his theories on light and color, and formulated the laws of planetary motion. These insights culminated in the publication of his seminal work, *Principia Mathematica*, which outlined his theory of gravity.

## Isaac Newton’s Laws of Motion

In 1687, Isaac Newton published *Philosophiæ Naturalis Principia Mathematica* (Mathematical Principles of Natural Philosophy), commonly referred to as the *Principia*. This work, resulting from 18 months of rigorous and continuous effort, is widely recognized as one of the most influential texts in the history of physics and possibly all of science. The publication of the *Principia* catapulted Newton to international prominence.

The Principia provides a precise quantitative description of the motion of bodies through three fundamental laws:

**First Law:** A body at rest will remain at rest, and a body in motion will continue in motion with a constant velocity, unless acted upon by an external force.

**Second Law:** The force exerted on an object is equal to its mass multiplied by its acceleration. Thus, a change in motion (i.e., a change in speed or direction) is directly proportional to the applied force.

**Third Law:** For every action, there is an equal and opposite reaction.

## Newton and the Theory of Gravity

Isaac Newton’s foundational work in *Principia Mathematica* laid the groundwork for his theory of gravity, which is rooted in his three fundamental laws of motion. Newton’s law of universal gravitation articulates that every two objects in the universe exert a gravitational force on each other. This force is directly proportional to the product of their masses and inversely proportional to the square of the distance separating their centers.

These principles not only elucidate the elliptical orbits of planets but also account for a broad spectrum of cosmic phenomena. They explain the maintenance of planetary orbits around the sun, the moon’s orbit around Earth, and the trajectories of Jupiter’s moons. Furthermore, they account for the elliptical paths of comets around the sun.

Newton’s laws enabled him to derive critical measurements such as the mass of each planet, the Earth’s polar flattening and equatorial bulge, and the gravitational influences of the sun and moon on Earth’s tides. In Newton’s framework, gravity serves as the fundamental force that orchestrates the cosmos, harmonizing celestial mechanics and terrestrial phenomena within a unified theoretical construct.

## Isaac Newton and Robert Hooke: A Historical Rivalry

Not all members of the Royal Society welcomed Isaac Newton’s groundbreaking work in optics, particularly his 1672 publication, Opticks: Or, A Treatise of the Reflections, Refractions, Inflections and Colours of Light. Among the critics was Robert Hooke, an eminent scientist and a founding member of the Royal Society, renowned for his contributions to mechanics and optics.

Newton posited that light was composed of particles, a theory that was at odds with Hooke’s wave theory of light. Hooke’s reaction to Newton’s paper was notably harsh; he criticized Newton’s methodology and conclusions with considerable disdain.

Hooke’s critique was particularly stinging due to his prominent role in the Royal Society and his own achievements in optics. Although other figures, such as the Dutch scientist Christiaan Huygens and various French Jesuits, also challenged Newton’s theories, Hooke’s criticisms had the most significant impact on Newton.

Newton’s response to Hooke’s criticisms was marked by indignation. Unable to tolerate the critique, Newton’s reaction was vehement, reflecting his general aversion to criticism throughout his life. He vehemently defended the validity of his work and emphasized its importance to the scientific community.

The contentious exchanges between Newton and Hooke intensified over the following months, leading Newton to consider resigning from the Royal Society. He ultimately remained, reassured by the support of other members who affirmed his esteemed status among the Fellows.

The rivalry persisted for several years until Newton suffered a severe nervous breakdown in 1678, which abruptly halted their correspondence. The subsequent death of Newton’s mother in 1679 led him to retreat further from public life, engaging minimally in intellectual discourse.

During this period of seclusion, Newton refocused on his study of gravitation and planetary motion. Ironically, Hooke’s own suggestion in a 1679 letter about planetary motion, involving an inverse square law, played a crucial role in guiding Newton’s research.

Although their correspondence resumed briefly, Newton soon discontinued it. Nevertheless, Hooke’s ideas on planetary motion significantly influenced Newton’s work. By 1680, Newton had independently developed his conclusions, though he kept them private.

In early 1684, Hooke presented his ideas on planetary motion to Royal Society members Christopher Wren and Edmond Halley. Both men found Hooke’s theories promising but noted the need for a mathematical demonstration.

In August 1684, Halley visited Newton, who had recently emerged from seclusion. When Halley inquired about the shape of a planet’s orbit if its attraction to the sun followed the inverse square law, Newton confidently responded with “an ellipse,” revealing his advanced understanding of the problem. Although Newton claimed to have solved the problem years earlier, he had misplaced his notes. Halley encouraged Newton to formalize his findings mathematically, funding the publication of these ideas in Newton’s *Principia Mathematica*.

Upon the publication of *Principia* in 1687, Hooke accused Newton of plagiarism, asserting that Newton had appropriated his theory of inverse squares. This accusation was largely dismissed by the scientific community, as Hooke’s work had not provided conclusive proof.

Newton’s response to Hooke’s accusation was one of outrage. He removed all references to Hooke from his notes and threatened to withhold the publication of future editions of *Principia*. Despite Halley’s efforts to mediate and reach a compromise, including a joint acknowledgment of Hooke’s contributions, Hooke remained unsatisfied.

As time progressed, Hooke’s life became increasingly troubled. The death of his niece and companion in 1687, coupled with Newton’s rising fame, deepened Hooke’s resentment. Hooke continued to antagonize Newton whenever possible and, knowing that Newton was poised to become President of the Royal Society, Hooke refused to retire until his death in 1703.

## Newton and Alchemy

Following the publication of *Principia Mathematica*, Isaac Newton sought a new direction in his life. His dissatisfaction with his role at Cambridge grew, prompting him to engage more actively in various political and intellectual issues.

Newton played a significant role in resisting King James II’s attempts to reintroduce Catholic teachings at Cambridge. In 1689, he was elected as a Member of Parliament for Cambridge. During his time in London, Newton expanded his intellectual circle and befriended prominent figures such as political philosopher John Locke. While many continental scientists continued to adhere to Aristotelian principles, a new generation of British scientists embraced Newton’s revolutionary views on the physical world, recognizing him as a leading figure in this emerging field. Among his admirers was Nicolas Fatio de Duillier, a Swiss mathematician who became a close friend.

Despite these achievements, Newton experienced a severe nervous breakdown in 1693. The exact cause of his breakdown remains uncertain. It could have been related to his frustration at not receiving a higher position under England’s new monarchs, William III and Mary II, or perhaps the deterioration of his friendship with Duillier. Other potential factors include exhaustion from overwork or chronic mercury poisoning resulting from years of alchemical research.

The letters Newton wrote to several London acquaintances during this period suggested paranoia and delusions, as he accused them of betrayal and conspiracy. However, Newton’s recovery was swift. He issued apologies to his friends and resumed his work within a few months. Despite regaining his intellectual acuity, Newton shifted his focus away from scientific endeavors and turned to the study of prophecy, scripture, and alchemy.

While this shift might seem incongruous for a figure who had revolutionized science, it reflects Newton’s engagement with the complex issues of 17th-century Britain. During this turbulent period, many intellectuals grappled with profound questions concerning religion, politics, and the purpose of life. Modern science was still in its nascent stages, leaving its relationship with traditional philosophies uncertain.

## Gold Standard

In 1696, Isaac Newton achieved the long-sought governmental position of Warden of the Mint. Following his appointment, he relocated permanently to London, where he resided with his niece, Catherine Barton.

Catherine Barton was the mistress of Lord Halifax, a prominent government official whose support was crucial in Newton’s subsequent promotion to Master of the Mint in 1699—a role he would hold until his death.

Determined to ensure that the position was not merely ceremonial, Newton approached his duties with rigorous commitment. He undertook significant reforms of the currency and implemented severe penalties for counterfeiters. One of his most notable achievements as Master of the Mint was the transition of the British currency from the silver standard to the gold standard.

## The Royal Society

In 1703, following the death of Robert Hooke, Sir Isaac Newton was elected President of the Royal Society. However, Newton’s tenure was marked by a lack of understanding of science as a collaborative endeavor. His ambition and staunch defense of his own discoveries frequently led to conflicts with fellow scientists.

Newton’s leadership at the Royal Society was characterized by autocracy and a domineering approach. He wielded considerable influence over the careers and research of younger scientists, often exercising his power with little regard for collegiality.

In 1705, a long-standing controversy erupted when German mathematician Gottfried Leibniz publicly accused Newton of plagiarizing his research. Leibniz claimed that he had developed infinitesimal calculus several years prior to the publication of Newton’s *Principia Mathematica*.

The Royal Society appointed a committee in 1712 to investigate the allegations. Given Newton’s position as President, he had the authority to appoint the committee members and oversee the investigation. It is not surprising that the committee’s findings ultimately upheld Newton’s claim to priority in the discovery.

In the same year, Newton was involved in another contentious episode. He published, without permission, the notes of astronomer John Flamsteed, who had amassed a significant body of data during his tenure at the Royal Observatory in Greenwich, England. Newton had requested Flamsteed’s notes for revisions to *Principia*. When Flamsteed did not provide the information promptly, Newton leveraged his position as President to become the chairman of the “visitors” overseeing the Royal Observatory.

Newton then attempted to force the immediate publication of Flamsteed’s star catalog and all of Flamsteed’s notes, both edited and unedited. Compounding the affront, Newton arranged for Flamsteed’s rival, Edmund Halley, to prepare the notes for publication.

Eventually, Flamsteed obtained a court order that compelled Newton to cease his plans and return the notes—one of the rare instances where Newton’s rival succeeded in challenging him.

## Final Years

In the later years of his life, Sir Isaac Newton resided at Cranbury Park, near Winchester, England, alongside his niece, Catherine Barton Conduitt, and her husband, John Conduitt.

By this period, Newton had achieved extraordinary prominence across Europe, renowned for his unparalleled scientific contributions. His financial acumen also ensured his considerable wealth, which he invested prudently and generously allocated to charitable causes.

Nevertheless, despite his considerable acclaim, Newton’s personal life was marked by solitude. He remained unmarried and had a limited social circle. In his twilight years, his character was characterized by a complex interplay of pride, insecurity, and idiosyncratic scientific pursuits. These traits, combined with his rarefied social interactions, led some of his few acquaintances to express concerns about his mental well-being.

## Death

By the age of 80, Sir Isaac Newton was grappling with significant digestive issues, which necessitated a considerable alteration to his diet and mobility.

In March 1727, Newton suffered a severe abdominal pain and subsequently lost consciousness. He remained in an unconscious state until his death on March 31, 1727, at the age of 84.

## Legacy

Isaac Newton’s legacy continued to flourish well beyond his death, with many of his contemporaries hailing him as perhaps the greatest genius of all time. While this accolade may be somewhat hyperbolic, the profound impact of his discoveries on Western intellectual history is undeniable, drawing comparisons to towering figures such as Plato, Aristotle, and Galileo. Despite the numerous advancements made during the Scientific Revolution, Newton’s formulation of universal gravitation stood uniquely influential, with no contemporary scientific theories offering a comparable framework.

It is important to note that Newton’s theories were not without their limitations. The 20th century saw Albert Einstein revolutionize our understanding of the cosmos, challenging Newton’s principles by demonstrating that space, time, and motion are relative rather than absolute, and revealing a universe far more complex than Newton had envisioned.

Reflecting on his achievements in later years, Newton displayed remarkable humility. When asked to assess his work, he famously remarked, “I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself now and then in finding a smoother pebble or prettier shell than ordinary, while the great ocean of truth lay all undiscovered before me.” This perspective underscores the ongoing quest for knowledge that characterizes the spirit of scientific inquiry.