Isaac Newton was, to put it bluntly, a bit of an oddball. He spent his time sticking needles in his own eyes for "science" and trying to turn lead into gold, but in between the weirdness, he basically rewrote the operating manual for the universe. Honestly, if you look at the sheer volume of what did sir isaac newton discovered, it’s a wonder the guy ever slept. Most of us know about the apple. It’s a classic story, right? He sits under a tree, fruit hits his head, and suddenly he understands gravity.
It didn't really happen like that.
The apple was more of a "spark" than a "bonk on the head." Newton himself told his biographer William Stukeley that he watched an apple fall and started wondering why it always went straight down, never sideways or up. That simple "why" led to a fundamental shift in how humans view existence. Before Newton, people thought the heavens and the Earth followed different rules. He was the one who realized they were the same.
The Law of Universal Gravitation: Bridging Earth and Space
When we ask what did sir isaac newton discovered, the big winner is always gravity. But it’s not just "things fall down." It’s the Universal Law of Gravitation. Newton published this in his 1687 masterpiece, Philosophiæ Naturalis Principia Mathematica. This book is a beast. It's thick, written in Latin, and incredibly dense, but it changed everything.
He proposed that every mass in the universe attracts every other mass. The moon stays in orbit because of the same force that makes a pen drop to the floor. This was heresy to some and revolutionary to everyone else. He used math to prove it, showing that the force is proportional to the product of the masses and inversely proportional to the square of the distance between them.
$$F = G \frac{m_1 m_2}{r^2}$$
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Think about that. One guy in the 17th century figured out the math that we still use to land rovers on Mars today.
The Three Laws of Motion (The Stuff That Makes Cars Move)
You can't talk about Newton without the three laws. These are the bedrock of physics.
- Inertia. An object stays still or keeps moving unless something hits it. Basically, things are lazy.
- F=ma. Force equals mass times acceleration. If you want a heavy thing to move fast, you gotta push it hard.
- Action and Reaction. For every action, there is an equal and opposite reaction.
These aren't just for textbooks. When you feel pushed back into your seat in a fast car, that’s Newton. When a rocket blasts fuel downward to go upward, that’s Newton. He didn't just "find" these; he codified them into a language that allowed engineers to build the modern world. It’s kinda wild that a guy who lived through the Great Plague of London is the reason we have safe elevators and high-speed trains.
Optics: The Man Who Cracked the Rainbow
For a long time, people thought white light was "pure" and color was something added to it by objects. Newton thought that was nonsense. In 1666, he hunkered down in a dark room, poked a hole in a shutter, and let a sliver of light hit a prism.
He saw a rainbow.
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But then he did something clever. He put another prism in front of that rainbow and turned it back into white light. This proved that white light is actually a messy, beautiful mix of all the colors. He discovered that light is made of particles—he called them "corpuscles"—and that different colors refract at different angles.
He also hated his telescopes. The ones they had back then used lenses that created a weird "halo" of color (chromatic aberration). So, he just built a better one. He invented the reflecting telescope, using mirrors instead of lenses. If you look at the Hubble Space Telescope or the James Webb, they are basically giant versions of the "Newtonian Reflector" he hand-built in his workshop.
He Literally Invented a New Kind of Math
Imagine you’re trying to calculate the speed of a falling object. It’s not moving at a constant speed; it’s accelerating. It’s changing every microsecond. Geometry and algebra couldn't really handle that "flow" back then.
So, Newton just invented Calculus. He called it "the method of fluxions."
He didn't even publish it right away because he was famously paranoid about people stealing his work. This led to a massive, bitter feud with Gottfried Wilhelm Leibniz, a German mathematician who also "invented" calculus around the same time. History generally gives them both credit now, but at the time, it was a total academic cage match. Without calculus, we wouldn't have modern economics, fluid dynamics, or even the algorithms that run your Instagram feed.
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The Weird Side: Alchemy and the End of the World
Newton wasn't just a cold, logical scientist. He was a man of his time. He spent more time writing about the Bible and alchemy than he did about physics. He studied the dimensions of the Temple of Solomon because he thought it contained a secret code for the universe.
He also predicted the world wouldn't end before 2060.
While that sounds "unscientific" today, it shows his mindset. He believed the universe was a giant clock built by God, and it was his job to figure out how the gears turned. This obsession is what drove him to stay up for days on end, skipping meals, just to solve a single math problem.
Why This Matters to You Right Now
Everything you do is governed by what did sir isaac newton discovered. When you hit the brakes on your bike, you're using his laws of friction and inertia. When you wear glasses, the lenses are designed using his optics. Your GPS works because engineers accounted for the gravitational pull Newton first described (with a bit of help from Einstein later, but Newton laid the foundation).
He was a complicated, often grumpy man who didn't like criticism. But he gave us a universe that was predictable. He took the "magic" out of the stars and replaced it with math. That transition is arguably the most important moment in human intellectual history.
Practical Steps to Explore Newton's Legacy
If you want to see Newton's work in action without becoming a physics professor, here is how you can actually engage with his discoveries:
- Watch a Newtonian Telescope in action: Search for "Newtonian vs. Refracting telescope" videos to see how his mirror design still provides the clearest views of deep space.
- Experiment with a prism: You can buy a cheap glass prism online. Replicate his 1666 experiment by splitting sunlight into a spectrum. It’s surprisingly satisfying to see it happen in person.
- Study the "Principia": You don't have to read the whole thing. Look up the "General Scholium" at the end of the book. It’s where Newton explains his philosophy and why he thinks the universe works the way it does.
- Track a satellite: Use an app like ISS Detector. The reason that hunk of metal stays in the sky without falling is entirely explained by Newton’s orbital mechanics.
Newton’s work reminds us that the universe isn't a series of random accidents. It follows rules. If you can understand the rules, you can change the world. He started with an apple and ended up giving us the stars.