View full lesson: http://ed.ted.com/lessons/why-are-man…
Why are most manhole covers round? Sure it makes them easy to roll, and slide into place in any alignment.
But there’s another, more compelling reason, involving a peculiar geometric property of circles and other shapes.
Marc Chamberland explains curves of constant width and Barbier’s theorem.
Lesson by Marc Chamberland.
Animation by Pew36 Animation Studios.