Home Educational Who decides how long a second is? – John Kitching Who decides how long a second is? – John Kitching Learning A New Way Jan 19, 2021 0 Comments Tweet on Twitter Share on Facebook Pinterest Check Out Our Recommended Resources Page See Some AMAZING Classes On DIY! atomic clock atomic time atomic time clock atoms cesium 133 cesium atom clock electromagnetic fields electron vibration electrons elemental isotope gregorian calendar international committee of weights and measures john kitching measure time pendulum periodic elements periodic table physics quantum mechanics second TED Ted Education TED-Ed Teded time timekeeping Tjoff Koong vaporized atoms