The atomic clock
Who
Isidor Isaac Rabi, an American Jewish physicist and Nobel laureate who first proposed timekeeping by atomic resonance
When
1945
Where
New York, United States
In 1945 Isidor Isaac Rabi proposed that the precise resonance frequency of atoms could serve as an extremely accurate clock, an idea that grew from his Nobel-winning work on magnetic resonance. Rabi was born to a Galician Jewish family and raised in an Orthodox home in New York; atomic clocks now define the second and make GPS possible.
Part of “The Gifts of the Jews” — verified Jewish contributions to the world, with sources.