Slinky escalator! What I like about this video (here’s the direct link so you can skip gizmodo: https://www.youtube.com/watch?t=12&v=5UP_njBPpZ4) is that it really shows the engineer’s thought process, iterating towards a successful solution with many (humorous) failures along the way.
Originally shared by Christian Brunschen
http://woodgears.ca/toys/slinky.html
(via http://toyland.gizmodo.com/actually-perpetual-slinky-escalator-is-humanity-s-grea-1721362441)