Richard Feynman: 2 ideas and puzzles worth knowing

2 ideas and puzzles from Richard Feynman, each explained in a minute and credited to the original work. Free on Savvy.

Feynman dunked an O-ring in ice water on live TV to expose Challenger's fatal flaw
During the 1986 hearings into the Challenger disaster, Feynman clamped a piece of rubber O-ring material, dropped it in his glass of ice water, and showed it lost its resilience in…
— Richard Feynman, Rogers Commission Report
Run a lawn sprinkler backward, sucking water in — which way does it spin?
A rotating sprinkler normally spins because water shoots out of its curved arms. Submerge it and make it suck water in instead, reversing the flow — does it spin the same direction…
— Ernst Mach (originator); popularized by Richard Feynman, Feynman sprinkler

Five ideas worth knowing, every week