Random number generation with lava lamps

Tom Scott explains how Cloudflare uses a wall of lava lamps to generate random numbers. A video camera is pointed at the wall, and the movement in the lamps plus noise from the video provides randomness, which is used to secure websites.

Even though computers can do many things on their own, they still need help from the physical world for true unpredictability. The robot overlords aren’t here yet. [via kottke]