A building block for GPS
As Harvard celebrates its 375th anniversary, the Gazette is examining key moments and developments over the University’s broad and compelling history. Next time your Global Positioning System (GPS) helps you get from point A to B without pulling out a map, thank Norman Ramsey. A professor emeritus of physics who recently died at 96, Ramsey’s work lay the foundation for the development of the atomic clock, a device that allows scientists to measure time more precisely than ever, and which is a critical component in global positioning systems (GPS). Just as a grandfather clock counts the oscillations of a pendulum to keep time, atomic clocks use the movement of atoms — which oscillate at precise frequencies — to measure time. Using the devices, a second is no longer measured as a fraction of the time it takes the Earth to revolve around the sun, but as the time it take a cesium-133 atom...