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Who decides how long a second is? - John Kitching

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5,403 Questions Answered

TEDEd Animation

Let’s Begin…

In 1967, researchers gathered to answer a long-running scientific question: just how long is a second? It might seem obvious at first. A second is the tick of a clock, the swing of a pendulum, the time it takes to count to one. But how precise are those measurements? And what is that length based on? John Kitching digs into how we scientifically define this fundamental unit of time.

How did ancient civilizations measure time?

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Meet The Creators

  • Educator John Kitching
  • Director Tjoff Koong
  • Narrator Addison Anderson
  • Animator Tezo Kyungdon Lee, Magnus Lenneskog
  • Sound Designer Stephen LaRosa
  • Director of Production Gerta Xhelo
  • Editorial Director Alex Rosenthal
  • Producer Bethany Cutmore-Scott
  • Editorial Producer Dan Kwartler
  • Script Editor Alex Gendler
  • Fact-Checker Eden Girma

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