cities

A short video from the trafficwaves.org site showing how traffic jams and standing waves form, including the fight between cheaters and blockers at an exit-lane backup. It also touches on how individual driving behavior affects the flow.

A short clip of Richard Feynman explaining how a train stays on its tracks, through the conical shape of wheels and how it handles curves without differentials.

A short clip from the 1983 BBC series Fun to Imagine in which Richard Feynman explains how a train stays on the track. He covers the geometry of tapered wheels that steer the train back toward the center of the rails.

A short clip from Carl Sagan's Cosmos in which he explains how Eratosthenes measured the circumference of the Earth using shadows in two Egyptian cities. It is a clear, visual account of an ancient scientific feat.