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| Isaac Newton revolutionized physics with his laws of motion and universal gravitation. This infographic covers his life, key discoveries, and lasting legacy. |
"In 1642, the year Galileo Galilei died, a baby so weak was born in a small English village that no one expected him to survive his first day. This baby was Isaac Newton – and he would change the course of science forever."
The Boy Who Shouldn't Have Survived
On Christmas Day 1642, a tiny and weak baby was born in the English hamlet of Woolsthorpe. He was so frail that he was not expected to survive his first day of life, much less 84 years . His father, also named Isaac Newton, had died three months before his birth . It was a beginning marked by loss and fragility, yet this child would grow up to become the culminating figure of the Scientific Revolution . His name was Isaac Newton, and his work would fundamentally change how humanity understands the universe.
Newton's early life was shaped by separation. When he was only two years old, his mother remarried and left him with his grandmother . This traumatic event may have contributed to the acute sense of insecurity he carried throughout his life, a trait that made him obsessively anxious when his work was published and irrationally violent when he defended it . As a young man, when examining the state of his soul, he even cataloged a childhood sin in shorthand: "Threatning my father and mother Smith to burne them and the house over them" .
It quickly became apparent that Newton was not suited for managing his mother's estate after her second husband died. He would curl up under a tree with a book, completely unable to concentrate on rural affairs . Fortunately, his family recognized his talents, and he returned to grammar school to prepare for the university. By June 1661, Newton was ready to matriculate at Trinity College, Cambridge .
Interesting Fact: The year of Newton's birth—1642—was also the year that Galileo Galilei died . One of the greatest minds of the Scientific Revolution was passing just as another was being born.
The Birth of a Genius
When Newton arrived at Cambridge in 1661, the curriculum was still rooted in the outmoded Aristotelianism that rested on a geocentric view of the universe . But the new philosophy of the Scientific Revolution was in the air. Newton soon discovered the works of the French philosopher René Descartes, whose mechanical philosophy viewed physical reality as composed entirely of particles of matter in motion .
Some time during his undergraduate career, Newton began a new set of notes entitled "Quaestiones Quaedam Philosophicae" ("Certain Philosophical Questions") . Under the title he wrote: "Amicus Plato amicus Aristoteles magis amica veritas" ("Plato is my friend, Aristotle is my friend, but my best friend is truth"). Newton's scientific career had begun .
Newton's mathematical education started with Descartes' La Géométrie and then branched out into the other literature of modern analysis. Within little more than a year, he had mastered the entire field and began to move into new territory . He discovered the binomial theorem and developed the calculus—a more powerful form of analysis that employs infinitesimal considerations .
By 1669, Newton was ready to write a tract summarizing his progress, De Analysi per Aequationes Numeri Terminorum Infinitas ("On Analysis by Infinite Series") . It circulated in manuscript and made his name known. Despite the fact that only a handful of savants were even aware of Newton's existence, he had become the leading mathematician in Europe .
The Plague Years: When Newton Changed the World
In 1665, the plague closed the University of Cambridge, and for the next two years, Newton was forced to stay at his home in Woolsthorpe . This period, known as his annus mirabilis, or "year of wonders," is one of the most remarkable episodes in the history of science.
During the plague years, Newton laid the foundations of the calculus . He extended his earlier insights into an essay, "Of Colours," which contained most of the ideas he would later elaborate in his Opticks . And he examined the elements of circular motion and applied his analysis to the Moon and the planets, deriving the inverse square relation that the radially directed force acting on a planet decreases with the square of its distance from the Sun—a crucial step toward the law of universal gravitation .
The world heard nothing of these discoveries at the time . Newton worked in isolation, letting his mind roam free across the landscape of physics and mathematics. He was just 23 years old.
Interesting Fact: The apple story? While there is no evidence that an apple actually fell on Newton's head, he did later recount that watching an apple fall from a tree helped him contemplate the nature of gravity and how it might extend to the Moon and planets.
The Principia: A New Physics
In 1684, Edmond Halley (who would later discover the comet that bears his name) visited Newton and asked what trajectory a body would follow under an inverse-square force . Newton replied immediately: an ellipse. Halley asked how he knew, and Newton said he had calculated it. After searching for his notes, Newton promised to send the calculation to Halley .
The intense effort that followed culminated in the publication of the Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) in 1687 . The Principia is considered one of the most important single works in the history of modern science . It is a deductive work in which, from very general propositions, mechanical properties are demonstrated in the form of theorems .
The Principia is organized into three books. Book 1, "Axioms and the Laws of Movement," is by far the best-known part . It contains Newton's three laws of motion, which form the foundation of classical mechanics :
First Law (Law of Inertia): A body remains at rest, or moves in a straight line at a constant speed, unless acted upon by a net outside force . In other words, every object continues to do what it happens to be doing unless a force is exerted upon it .
Second Law (F = ma): Force on a body causes it to accelerate in the direction of the force. The acceleration is proportional to the strength of the force and inversely proportional to the mass of the body . This is the fundamental equation of classical mechanics: F = ma .
Third Law (Action and Reaction): Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body . This is sometimes phrased as: "For every action, there is an equal and opposite reaction" .
Book 2 deals with the movement of bodies in relation to resistance and velocity . Book 3, "The System of the World," applies the principles of astronomy Newton had developed. He explores derivation of the laws of gravity, implications for planetary orbits, and the study of comets .
Light, Color, and the Reflecting Telescope
Newton's work in optics was equally revolutionary. Through a series of experiments performed in 1665 and 1666, in which he projected the spectrum of a narrow beam of sunlight onto the wall of a darkened chamber, Newton fundamentally changed the understanding of light and color .
The ancient theory, extending back at least to Aristotle, held that white light was simple and homogeneous and that colors arose from the modification of light . Newton denied this concept. He concluded that white light is complex and heterogeneous—a mixture of all the colors—and that the phenomena of colors arise from the analysis of this heterogeneous mixture into its simple components .
He also concluded that rays refract at distinct angles—hence, the prismatic spectrum—and that phenomena such as the rainbow are produced by refractive analysis . Because he believed that chromatic aberration could never be eliminated from lenses, Newton turned to reflecting telescopes and constructed the first ever built . The heterogeneity of light has been the foundation of physical optics since his time .
The Later Years: A Life of Achievement and Controversy
Newton's later years were marked by public service and acrimonious disputes. He moved to London in 1696 to serve as Warden of the Royal Mint, and three years later became Master of the Mint . He was knighted in 1705 .
He was elected President of the Royal Society in 1703, a post he held until his death . During his London years, he engaged in a bitter dispute with Gottfried Leibniz over who had priority for inventing the calculus . One element fueling this dispute was Newton's failure to publish his work on the subject; his first formal publications on the calculus did not appear until 1704 .
Newton articulated a broadly empiricist philosophy of science, explicitly in his "Rules of Reasoning in Philosophy" at the beginning of Book 3 of the Principia, and implicitly in his derivation of the inverse square law from astronomical data . He rejected speculations unproductive unless informed by experiment .
Interesting Fact: Newton died in London in 1727 at the age of 84—a remarkable lifespan for the era. He was buried in Westminster Abbey, the first scientist to receive such an honor.
Conclusion: The Universe Unlocked
Newton once famously said: "If I have seen further, it is by standing on the shoulders of giants" . While humble, this statement acknowledged his debt to Kepler and Galileo . The work that Newton accomplished—the laws of motion, the law of universal gravitation, the theory of light and color, the invention of the calculus—constituted what many consider the greatest contribution of any single scientist in history.
Isaac Newton died on March 20, 1727 , leaving behind a world transformed. He set down the fundamental principles that would define physics for centuries . He was not simply a physicist or a mathematician—he was a theologian, alchemist, and a man who sought to understand the deepest mysteries of existence .
In the words of the French mathematician Alexis Clairaut: "The famous book of Mathematical Principles of Natural Philosophy marked the epoch of a great revolution in physics. The method followed by its illustrious author Sir Newton... spread the light of mathematics on a science which up to then had remained in the darkness of conjectures and hypotheses" .
Newton gave us a universe that could be understood, measured, and predicted. He gave us the laws that govern the fall of an apple and the orbit of a planet. He unlocked the universe—and we have been exploring it ever since.
Sources and Further Reading
Encyclopædia Britannica. Isaac Newton: Biography, Facts, Discoveries, Laws, & Inventions. https://www.britannica.com/biography/Isaac-Newton
Ohio State University. Newton's Laws of Motion. https://www.astronomy.ohio-state.edu/weinberg.21/A161/lecture8.html
Brilliant. Newton's Laws of Motion. https://brilliant.org/wiki/newtons-laws-of-motion/
Routledge Encyclopedia of Philosophy. Newton, Isaac (1642-1727). https://www.rep.routledge.com/articles/biographical/newton-isaac-1642-1727/v-1
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