Physics is the rulebook of the universe — the surprisingly short list of rules that decide why things fall, fly, float, glow, and go bang. The jaw-dropping part is that the same rules run a pencil rolling off your desk, a rocket to Mars, and a star a billion light-years away. Crack the rules once and you understand all three.

It runs on maths

Physics runs on mathematics. A law of physics is usually just an equation — and because the maths is exact, it can predict the future: aim Newton's

at a cannonball and it tells you precisely where the ball will land before you've even lit the fuse. Einstein's E = mc^2 is the same trick on a grander scale — three little letters that unlock the energy inside an atom.

When the maths gets too wild

Some systems are far too tangled to solve with pen and paper — the weather, a swirling galaxy, the inside of a star. So physicists hand them to computer science and let a machine grind through the numbers, step by tiny step. Every weather forecast and every video-game explosion is really physics, simulated.

Physics on the Primer is just getting started — here's what's on the roadmap.