difference engine

Part 10 of Dan Gelbart's prototype-building lecture series, covering flexures: flexible joints that give precise, frictionless motion. It shows how a cheap piece of aluminum can become a nanometer-accurate mechanism.

A short clip of Richard Feynman on the difference between merely knowing how to reason mathematically and understanding why physical theories work. He discusses holding multiple equivalent ideas and guessing new laws.

An excerpt from Hal Abelson's opening SICP lecture introducing computer science and contrasting declarative and imperative knowledge. He argues that computer science is not really a science and is more like magic or engineering of ideas.