Isaac Newton’s Philosophiæ Naturalis Principia Mathematica, (Latin for “Mathematical Principles of Natural Philosophy”) was published 325 years ago today, on 5 July 1687. This is the book that laid out Newtonian Physics.
It’s an astonishing book. In the section on the orbit of the planets and their moons, Newton showed that gravity depends on the square of the distance between massive bodies, and that the gravity acts as though it’s all concentrated in the centre of the body.
In the process he invented calculus to explain the speed of a planet along its orbit. (Planets move faster when they’re closest to the sun.) That would have been a major work in itself, but it’s book 1 of 3.
Book 2 is about the movement of bodies where there’s friction. It shows that resistance to motion is proportional to the square of the velocity.
Book three explains oddities in the moon’s orbit and the tides on Earth – each causes the other. And the trajectory of comets.
And all this stayed completely unchallenged for 218 years until Einstein proved that it didn’t apply in extreme conditions. As Neil DeGrasse Tyson says, “Newton Da Man.”
