John Kitching: Who decides how long a second is?

Who decides how long a second is?

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 length of a second is no longer just a tick of a clock or a swing of a pendulum. In 1967, scientists agreed to anchor this vital unit of time to the vibrations of a cesium-133 atom, which ticks over nine billion times per second. This switch from astronomy to atomic physics gave humanity a universal standard, ensuring that every clock on Earth—and even in space—can stay perfectly synchronized. Today, atomic clocks guide everything from global positioning systems to radio signals.