GUY RAZ, HOST:
If you want to know what time it is, a smart way to do so is call the U.S. Naval Observatory here in Washington, D.C.
(SOUNDBITE OF USNO TIME SERVICE)
ROBERT SIEGEL, HOST:
We owe this accurate timekeeping to a man named Norman Ramsey. Ramsey died Friday at age 96. It was his scientific research in the years following World War II that revolutionized how we keep track of time.
RAZ: Now, before his breakthrough, clock time was based on the age-old observation of the Earth whirling around the sun. That gave us the year. We divided that into days, hours, minutes, seconds, Norman Ramsey changed that.
SIEGEL: After the Second World War, Ramsey found himself at Harvard experimenting with measurements of electromagnetic radiation being absorbed by molecules and atoms. From this, the idea of an atomic clock was born. We no longer looked up to the cosmos for time, instead we drilled down to the inner workings of the cesium atom. Deep in that atom, a pulsating nine billion oscillations per second provided a new basis for clock time.
RAZ: By the way, Ramsey's research wasn't just useful in clocks. It also led to nuclear magnetic resonance, the machines we know as MRI used by doctors. Later in his career, Ramsey helped found the world renowned Fermilab in Chicago. Adrienne Kolb is Fermilab's historian. She says Ramsey was instrumental in convincing the federal government to support the research there.
ADRIENNE KOLB: Norman, with his sensitivities for a national laboratory, was able to reach out to everyone and convince them that this was the way to go. That we needed a national laboratory to allow the researchers throughout the country and indeed the world to operate at the highest energies to produce next generation of scientists for America.
SIEGEL: She was speaking of Norman Ramsey, 1989 Nobel Laureate in Physics and the father of the atomic clock. He died Friday at his home in Massachusetts at age 96. Transcript provided by NPR, Copyright NPR.