Physics explained
in motion.
From pendulums to planets — real physics, real simulations, no videos.
Six branches of physics.
Start with what exists. The rest is on the way.
CLASSICAL MECHANICS
The physics of cannonballs, planets, and pendulums.
ELECTROMAGNETISM
Light, charge, and the field that holds the world together.
THERMODYNAMICS
Heat, entropy, and why time moves forward.
RELATIVITY
The weirdness that hides at the edges of speed.
QUANTUM MECHANICS
The rules the universe actually runs on.
MODERN PHYSICS
From the nucleus to the Standard Model and beyond.
Start here: The Pendulum.
The pendulum is the first serious toy physics ever gave us. It was how Galileo discovered that time could be measured by motion, and how three hundred years of clocks kept pace with the turning of the Earth.
Its motion looks simple — a bob swinging back and forth — but hiding inside that swing is the most important equation in all of oscillations. Pull it out, and you get music, lasers, bridges, and the guts of quantum mechanics.
Three rules for every topic.
Real math, not cartoons.
Every animation is driven by a unit-tested physics solver — odex for ODEs, Newton-Raphson for Kepler's equation, analytic solutions where they exist. If a number appears on screen, it's correct to at least three decimals.
Feel it before you prove it.
We show you the idea first, with moving pictures, and the math second. No formulas without a picture. No picture without the math underneath.
Free and open source.
Every line of code, every equation, every solver — open source. Fork it, embed it, improve it. Society gets smarter when physics gets easier.