Atomic Clocks - The Best Timekeepers

Time is a fundamental physical quantity and the second is one of the seven base units in the International System of Units. In 1967, the second was redefined as “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.” Except for a little rewording, that definition still remains in place. The most accurate timekeeping devices are atomic clocks. The current cesium fountain clocks would neither gain nor lose a second in more than 100 million years; yet, scientist are trying to make more accurate clocks. That is because more accurate time measurement would lead to valuable scientific and engineering applications – examples include: placing bounds on the variation of fundamental constants of Nature and developing GPS systems with sub-centimeter accuracy. In this talk, I’ll present an overview of how 3 common types of atomic clocks work.