Isaac Newton is probably one of the smartest people of all time. Aside from discovering the foundations of physics, he was also the first person to describe the force of gravity. He designed the first practical reflecting telescope and explained how colours work based on the phenomenon of white light splitting into a rainbow after passing through a prism. He has been credited with inventing ridge-edged coins (to fight counterfeiting) and the cat-flap door (seriously), and was an influential religious philosopher. But my favourite story about Newton is the following.

Around 1666, Newton locked himself in his room for a while and, basically, invented calculus.^{[1]}Calculus is a set of concepts and techniques, completely new to the usual addition-subtraction-multiplication kind of math, which allowed people to finally use numbers to describe changes — like the change of position (velocity) or the change of velocity (acceleration). But despite the enormous importance of this invention, for some reason, Newton didn’t tell anyone about it for years afterwards. He mentioned some of the basics in an annotation to a footnote somewhere, and actually used calculus in his major physics works, but never published the original paper on calculus itself. A few years later, a man named Gottfried Wilhelm Leibniz also invented calculus, completely independently of Newton’s work. Newton got fairly upset about this, accusing Leibniz of plagiarizing from, well, the papers that he had failed to show anybody.

Today, both men are credited with inventing calculus, although Leibniz’s firmer grasp of publicity earned him the small victory of having his notation, rather than Newton’s, live on in mathematics even today.

But despite the man’s peculiarities, without Newton’s work, physics would not be anywhere near the point it is at today.

Newton described his laws of motion in a 1687 work with the catchy title *Philosophiæ Naturalis Principia Mathematica*, which stayed at the top of the New York Times bestseller list for over three weeks (a record at the time). This book remains one of the most important scientific works in human history. In it, he famously used his laws of motion in combination with a new theory of gravity to explain the movement of the stars and planets (more on this in the chapter on gravity). Newton thus brought new mathematical insights to problems that had been baffling humanity for ages and effectively founded an entire branch of physics, now known as classical mechanics.

In order to fully understand each of the three laws, we’ll need to spend a bit of time explaining what a force is.

- If any math historians are currently reading this, please forgive the impreciseness in this paragraph. ↩

I love his hair!

It’s funny how similar the invention of calculus story is to the story of the discovery of natural selection by Darwin and Wallace. Apparently good ideas have due dates?

I have much love for your use of a proper ash. Character map, people! It’s not hard.