08-27-2014 is Norman Foster Ramsey's aniversary

Born 27 Aug 1915; died 4 Nov 2011 at age 96.

Norman Foster Ramsey was an American physicist who shared (with Wolfgang Paul and Hans Georg Dehmelt) the 1989 Nobel Prize for Physics in 1989 for “for the invention of the separated oscillatory fields method and its use in the hydrogen maser and other atomic clocks.” 

His work produced a more precise way to observe the transitions within an atom switching from one specific energy level to another. In the cesium atomic clock, his method enables observing the transitions between two very closely spaced levels (hyperfine levels).


The accuracy of such a clock is about one part in ten thousand billion. In 1967, one second was defined as the time during which the cesium atom makes exactly 9,192,631,770 oscillations. 

 Prof. Sérgio Torres