If you’ve ever sat through a high school physics class, you’ve heard the name. Isaac Newton. The guy with the apple. The genius who basically "invented" gravity while sitting in a garden avoiding the plague. But the actual book he wrote to explain it all, the Philosophiæ Naturalis Principia Mathematica—or just Isaac Newton the Principia for those of us who don't speak fluent 17th-century Latin—is a whole different beast. It’s not just a textbook. It’s arguably the most influential document in the history of human thought, and honestly, it’s also one of the most difficult, dense, and drama-filled pieces of writing ever published.
Most people think Newton just woke up, saw an apple fall, and jotted down some notes. Not even close.
The story behind the Principia is a mess of petty rivalries, near-bankruptcy, and a random astronomer named Edmond Halley basically begging Newton to stop being a hermit and share his work with the world. Without Halley, this book probably would have stayed locked in Newton’s desk at Cambridge, and we’d still be wondering why the moon doesn't just fly off into deep space.
The Most Expensive "No" in Scientific History
The Royal Society was supposed to publish the book. That was the plan. But they had just spent their entire budget on a super fancy, illustrated book called History of Fishes, which, as it turns out, was a total commercial flop. They were so broke they couldn't afford to print Newton’s masterpiece. In fact, they ended up paying Edmond Halley his salary in leftover copies of the fish book.
Imagine that.
Halley had to pay for the printing of Isaac Newton the Principia out of his own pocket. He also had to act as Newton’s editor, cheerleader, and diplomat. Newton was notoriously prickly. He hated criticism. He hated people. If Halley hadn't been there to stroke Newton’s ego and keep him focused, the foundations of modern physics might have been lost to a mid-life crisis and a sudden interest in alchemy.
🔗 Read more: Why the Gun to Head Stock Image is Becoming a Digital Relic
What’s Actually Inside the Principia?
It’s divided into three "books."
Book 1 is where Newton lays out the laws of motion. You know these. Inertia ($F = ma$), and the idea that every action has an equal and opposite reaction. But he doesn't just list them. He proves them using geometry. This is the weird part for modern readers. Newton had already invented calculus—he called it the "method of fluxions"—but he didn't use it in the Principia. He thought geometric proofs were more elegant and harder to argue with. It’s like using a hand-saw to build a skyscraper just to prove you can.
Book 2 is a bit more obscure. It deals with fluids. He wanted to disprove René Descartes’ theory that the planets were carried around by giant celestial whirlpools or "vortices." Newton basically used math to bully Descartes’ theory out of existence. He showed that the resistance of a fluid would eventually slow down the planets, which clearly wasn't happening.
Then comes Book 3: The System of the World.
This is the big one. This is where he takes the math from the first two books and applies it to the entire universe. He shows that the same force that makes a stone fall to the ground in London is the exact same force that keeps the Moon in orbit. This was a radical idea. Before Isaac Newton the Principia, people thought the heavens and the Earth operated under different rules. Newton unified them. He turned the universe into a giant, predictable clock.
💡 You might also like: Who is Blue Origin and Why Should You Care About Bezos's Space Dream?
The Controversy You Never Hear About
Newton didn't work in a vacuum. Robert Hooke, a brilliant but equally grumpy scientist, claimed he gave Newton the idea for the inverse-square law of gravity. Hooke was furious. He wanted credit. Newton, being Newton, reacted by scrubing almost every mention of Hooke from the final manuscript. He literally tried to erase the guy from history.
There’s also the "General Scholium." This is a section Newton added to later editions because people were complaining that his theory didn't explain what gravity actually was. They called it "occult." Newton’s response? Hypotheses non fingo. "I frame no hypotheses." Essentially, he was saying: "I don't know why it happens, I just know the math works. Deal with it."
Why It Still Matters for You
You might think 300-year-old math is irrelevant. It isn't. Every time you use GPS, you’re relying on the physics laid out in this book. Every satellite launch, every bridge built, every flight you take—it all traces back to the three laws of motion.
But there’s a limit.
Newton’s universe is "flat." It’s absolute. He thought space and time were fixed stages where things happened. We now know, thanks to Einstein, that space and time are actually flexible. Newton’s math breaks down when you get close to a black hole or start moving at the speed of light. But for almost everything else—from driving a car to landing a rover on Mars—Newton is still the king.
📖 Related: The Dogger Bank Wind Farm Is Huge—Here Is What You Actually Need To Know
How to Actually "Read" the Principia (If You’re Brave)
- Don’t start with the Latin. Find a modern translation. The 1999 translation by I. Bernard Cohen and Anne Whitman is the gold standard.
- Skip the math at first. Read the "Definitions" and the "Axioms, or Laws of Motion." They are surprisingly readable.
- Look at the diagrams. Newton’s visual logic is fascinating. You can see him trying to "see" gravity through circles and triangles.
- Read the "General Scholium" at the end. It’s where Newton gets philosophical and even a bit religious. It gives you a glimpse into his actual mind, rather than just his calculator.
Taking Action: The Newtonian Mindset
If you want to apply the logic of Isaac Newton the Principia to your own life or work, start with the first law: things in motion stay in motion. Friction is the enemy. In business or personal habits, the hardest part is always the initial "push." Once you have momentum, Newton’s math says it’s much easier to keep going.
Secondly, understand that complexity often hides simple rules. Newton took the messy, chaotic movement of the stars and reduced it to a few lines of math. When you're overwhelmed by a project, look for the "universal" rule governing it. Usually, there are only two or three variables that actually matter. The rest is just noise—or as Newton might say, just a bunch of "fish books" getting in the way of the truth.
To truly understand the impact of this work, visit the Royal Society’s digital archives or check out the digitized version of Newton’s own annotated copy of the Principia held at Cambridge University. Seeing his handwritten notes in the margins—where he’s correcting his own genius—is a reminder that even the most world-changing ideas started as a messy first draft.
Move toward your goals by identifying the "centripetal forces" in your life—those things that pull you toward your center—and use that gravity to stay on track. Physics isn't just for planets; it's a manual for how to move through the world with intent.