Learn · TED

Talk6 min

Who decides how long a second is?

John Kitching · TED

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About

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. [Directed by Tjoff Koong, narrated by Addison Anderson].

The talk

  1. Who decides how long a second is? 6 min · TED's player

Credits and licence

Institution
TED
Department
TED-Ed
Speaker
John Kitching
Year
2021
Level
For everyone
Language
English
Subjects
Physics, History, Teaching and learning
Source
TED
Licence
CC BY-NC-ND 4.0, as TED states it. Non-commercial use only, and no changed versions. TED's terms
Attribution
TED Talks are licensed by TED under Creative Commons BY-NC-ND 4.0 International and are shown here in TED's own player, as TED's usage policy asks.
Who can watch
TED gives no rating. Invisible Network shows it to Teens profiles and older, judged from what the source says about it. How courses are placed