His wife says the emeritus professor of physics at Harvard University died in his sleep at a Wayland nursing home on Friday.

Ramsey wrote in his autobiography for the Nobel Prize he shared with Hans Dehmelt and Wolfgang Paul that he was inspired by failure in molecular beam magnetic resonance experiments to invent a new technique of measuring the frequency of radiation from atoms.

His method was used to develop the world's most accurate timekeeper, the atomic clock.
Ramsey taught at Harvard for four decades. During World War II, he worked on the Manhattan Project.