約翰·基欽: 誰決定一秒有多長?

誰決定一秒有多長?

1967 年，研究者齊聚一堂，試圖解答一個長久以來的科學問題：究竟一秒有多長？起初，答案似乎很明顯。一秒鐘是時鐘滴答了一聲、鐘擺搖動一下，或是數到一的時間。但是這些測量方法真的準確嗎？他們又是以什麼為基準來決定一秒的長度呢：跟著約翰·基欽（John Kitching）探索我們如何以科學方法定義時間的基本單位。

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.