Sound

Bartosz Ciechanowski's article on sound begins where sound itself begins: with air molecules jostling in a tiny cube. From that cube it grows into waves, frequencies, spectra, and the ear — each step accompanied by a widget you can play or manipulate.

The result is a physics lesson that behaves like an instrument. You hear compression and rarefaction, see how a Fourier series assembles a square wave, and feel why the same vibration can be noise in one context and music in another.