What Were Isaac Newton's Key Discoveries? Exploring 10 of His Revolutionary Inventions

While many recognize Sir Isaac Newton (1642-1727) as the "apple and gravity" figure, the epitaph on his tomb at Westminster Abbey reveals a legacy of extraordinary achievements:

Even by the standards of epitaphs, the level of admiration expressed here is extraordinary. What groundbreaking discoveries did Isaac Newton make to earn such high regard?

Born to an illiterate farmer, Newton rose to become a true Renaissance man — a revered expert in astronomy, chemistry, mathematics, physics, and theology. His insatiable curiosity drove him to address issues ranging from the trivial, like cats urinating on rugs, to the profound, such as humanity's role in the universe.

Newton's groundbreaking discoveries, innovative inventions, and bold ideas offer a window into the workings of a genius mind.

10. Newton's Orbital Cannon

Though the story of Newton and the apple tree is often dismissed as folklore, it pales in comparison to his profound insights into the mechanics of gravity. In formulating his law of universal gravitation, Newton envisioned an enormous mountain so tall that its peak reached into space, where he imagined placing a massive cannon.

Contrary to popular belief, Newton's orbital cannon wasn't designed to combat extraterrestrial threats. Instead, it served as a conceptual tool to illustrate how objects could orbit one another. If the cannonball was fired with too little or too much gunpowder, it would either plummet back to Earth or escape into space.

However, with the perfect amount of gunpowder, the cannonball would achieve just the right speed to fall toward Earth at the same rate the planet's surface curves away. This balance, Newton explained, would allow the cannonball to remain in perpetual free fall, effectively orbiting the Earth.

Introduced in 1687, Newton's law of universal gravitation proposed that every particle exerts a gravitational pull. This force, influenced by mass and distance, governs everything from falling rain to the motion of planets.

Although Einstein later refined aspects of Newton's gravitational theory, the 16th- and 17th-century physicist laid the essential foundation for our contemporary understanding of gravity.

9. Newtonian Cat Doors

When not occupied with conceptualizing space cannons or deciphering the forces that bind the cosmos, Isaac Newton directed his genius toward more mundane challenges — like preventing cats from scratching doors.

Newton had few close relationships and remained unmarried, but he did share his life with cats and dogs. Accounts of his bond with animals vary; some modern historians describe him as an animal enthusiast, while others recount questionable stories about a dog named Diamond. Some even dispute whether he had pets at all.

Legend has it that during his time at the University of Cambridge, Newton's experiments were frequently disrupted by his cats scratching at his office door. To solve this, he called upon a local carpenter to cut two holes in the door: a larger one for the mother cat and a smaller one for her kittens. However, since the kittens simply followed their mother through the larger hole, the smaller one remained unused.

"Whether this tale is true or not, it is undeniable that the door still bears two plugged holes of appropriate sizes for a cat and her kittens," wrote a contemporary of Newton years after the scientist's passing.

The truth of this story remains uncertain. Newton may have created one of the most beloved cat accessories in history — or someone at Cambridge simply enjoyed drilling random holes.

8. Laying Down the Three Laws of Motion

Newton's impact on modern physics is undeniable. Just as he deciphered gravity's fundamentals in his law of universal gravitation, he also unraveled the essence of motion with his three laws of motion in 1687. Here's a breakdown of these principles:

While these laws may seem obvious today, scholars struggled with the basics of motion for centuries. Aristotle, for instance, believed smoke rose because it was mostly air and thus chose to ascend to join its air companions in the sky.

René Descartes, the French philosopher, formulated motion laws resembling parts of Newton's first and third laws, yet he attributed the initial impulse to God.

Elegant in their simplicity, Newton's three laws allow scientists to comprehend the motion of entities ranging from subatomic particles to vast galaxies.

7. The Philosopher's Stone

Newton's insatiable thirst for knowledge drove him to countless scientific breakthroughs, but it also led him down a futile path: the pursuit of alchemy's mythical philosopher's stone.

Accounts of the philosopher's stone vary, but it was essentially a man-made substance believed to grant universal transformation. It could allegedly turn lead into gold, heal diseases, and even convert a headless cow into a swarm of bees.

Why would one of history's greatest scientific minds delve into alchemy?

To understand this, consider that the scientific revolution was still emerging in the 1600s. Alchemy had not yet been dismissed as pseudoscience, and despite its mystical elements, alchemical writings often explored genuine chemical processes.

Decades of Newton's experimental notes reveal his ambitions extended beyond mere chemistry or the allure of gold. Historian William Newman suggests he sought "unlimited dominion over nature."

This pursuit led Newton to study texts on the philosopher's stone, which he tried to decipher to create the elusive substance. Though his efforts were unsuccessful, he did produce a purple copper alloy. While not an invention, the stone sheds light on Newton's mindset and the era in which he lived.

In 2005, historian Newman recreated the same stone by following Newton's 300-year-old instructions. No transformations were observed.

6. Advanced Mathematical Principles

Whether your high school calculus class fascinated or overwhelmed you, you can attribute it to Isaac Newton. Mathematics serves as the framework for understanding the universe's mechanics, but like many scientists of his time, Newton discovered that existing algebra and geometry fell short of meeting his scientific demands.

Take a moment to absorb this: The mathematical tools available at the time were insufficient for Newton's needs.

Mathematicians back then could determine a ship's speed but couldn't calculate its acceleration. They could measure the angle of a cannonball's trajectory but couldn't identify the optimal angle for maximum distance. What they lacked was a mathematical framework to solve problems involving dynamic variables.

This was the challenge Newton faced when the bubonic plague struck England in the spring of 1665. As the plague ravaged the population, Cambridge shut down, and Newton spent 18 months developing the foundations of what he termed "the science of fluxions."

Today, we recognize this as calculus, an essential tool for physicists, economists, and probability experts. In the 1960s, it even helped Apollo engineers map a trajectory from Earth to the moon.

Of course, Newton doesn't deserve sole credit. He shares this achievement with German mathematician Gottfried Leibniz, who independently formulated calculus around the same period.

5. Rainbows and White Light

Did you think your mysteries were safe from Isaac Newton, rainbows? Think again, because in 1704, he authored the definitive work on light refraction. Titled "Opticks," this groundbreaking book revolutionized our understanding of light and color.

While scientists of the time understood that rainbows resulted from light refracting and reflecting through raindrops, they couldn't explain their vibrant colors. When Newton began his studies at Cambridge, the prevailing theory was that water somehow tinted the sun's rays with various hues.

Newton conducted experiments using a lamp and a prism, passing white light through the prism to split it into a spectrum of colors. While the prism technique wasn't new, scientists believed the prism added color to the light. By redirecting the separated light through a second prism, Newton recombined it into white light, demonstrating that the colors were inherent to the light itself.

4. Newton and the Reflecting Telescope

Newton entered a world where telescopes were far from perfect. Even the better models relied on glass lenses to magnify images. Through his color experiments, Newton understood that lenses refracted different colors at varying angles, resulting in blurred images for observers.

To enhance telescope design, Newton suggested replacing refracting lenses with reflecting mirrors. A large mirror would capture the image, and a smaller one would direct it to the viewer's eye. This approach not only delivers sharper images but also enables the creation of more compact telescopes.

While a Scottish mathematician initially proposed the concept of a reflecting telescope, Newton was the one who took the initiative to construct it.

Newton personally crafted the mirrors, creating a prototype that he showcased to the Royal Society in 1670. Measuring just 6 inches (15 centimeters), the device eliminated color distortion and offered 40x magnification.

Even today, most astronomical observatories utilize a version of Newton's reflecting telescope.

3. Newton Perfected Coinage

By now, you likely understand Newton's meticulous personality. It shouldn't be surprising, then, that when he was appointed to the largely ceremonial role of Warden at the Royal Mint in 1696, the renowned scientist took to London's streets — in disguise — to hunt down counterfeiters.

Yes, Isaac Newton was essentially the 17th-century equivalent of Batman.

Given that counterfeiting was a capital crime in Britain at the time, the criminals he apprehended often met their end at the execution block.

By the late 1600s, England's financial system was in complete disarray. The nation's currency consisted solely of silver coins, and the silver itself was often more valuable than the coin's face value. As a result, people melted down the coins or clipped silver from the edges to sell to France.

By Newton's era, clipping had severely damaged the country's currency. A typical bag of English coins was a chaotic mix of damaged and unrecognizable silver pieces. This made counterfeiting rampant, as the inconsistent size and quality of coins made it easy to pass off even poorly made fakes as genuine currency.

Public trust in the English currency collapsed, leading to widespread riots.

In 1696, the British government turned to Newton. Beyond his hands-on efforts to combat crime, he ordered all English coins to be recalled, melted down, and remade into a more durable, counterfeit-resistant design.

This was a drastic measure, as the country had to function without a currency for an entire year. Working up to 18 hours a day, Newton transformed the Royal Mints into efficient, high-quality factories producing coins that were nearly impossible to counterfeit.

Have you noticed the ridges on the edge of a U.S. quarter? These are milled edges, a design introduced by Newton on English coins to prevent silver clipping.

2. Newton's Law of Cooling

As you might have guessed, Isaac Newton's idea of relaxation involved diving deep into scientific or even occult challenges with his immense intellect. When existing tools, methods, or laws fell short, he created new ones. You could say he was the Chuck Norris of the scientific world.

If you've ever left a half-finished cup of coffee and returned to find it cold, you've experienced the process of cooling. Newton, however, was fascinated by the physics behind that cooling process.

In the late 1700s, he conducted experiments with red-hot iron balls. He observed that when the temperature difference between the ball and the surrounding air was less than 50 degrees Fahrenheit (10 degrees Celsius), the rate of heat loss was directly proportional to that temperature difference.

This led to Newton's law of cooling, which states that the rate at which a body loses heat is proportional to the temperature difference between the body and its environment.

French chemist Pierre Dulong and physicist Alexis Petit later refined the law in 1817, but Newton's foundational work on cooling remains critical in fields ranging from nuclear reactor safety to space exploration.

1. Newtonian Apocalypse

Humans have always been anxious about the end of the world, but Isaac Newton wasn't one to take apocalyptic predictions at face value. When 18th-century fearmongers made biblical claims about the end times, he turned to research and fact-checking.

Newton was deeply knowledgeable about theology. His relentless, problem-solving nature drove him to explore not only the secrets of alchemy but also the enigmatic visions described in the Book of Daniel.

Newton firmly believed the Bible held ancient, undeniable wisdom, if only scholars could decipher its codes. However, 300-year-old documents suggest his main goal in studying the Book of Daniel was to debunk the fearmongers.

Newton predicted the end of the world would occur in 2060 — possibly later, but certainly not before. Essentially, he was saying, "Move along, folks, there's nothing to worry about yet."

At least, that's what he assured his 18th-century contemporaries. You, however, might have a different perspective on the matter.