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Device That Revolutionized Timekeeping Receives an IEEE Milestone

The atomic clock, invented in 1948, paved the way for GPS

3 min read
Edward U. Condon [left], director of the National Bureau of Standards, with Harold Lyons, inventor of the ammonia absorption cell atomic clock [above].
Edward U. Condon (left), director of the National Bureau of Standards, with Harold Lyons, inventor of the ammonia absorption cell atomic clock (above).
Photo: IEEE

THE INSTITUTEThe invention of the atomic clock fundamentally altered the way that time is measured and kept. The clock helped redefine the duration of a single second, and its groundbreaking accuracy contributed to technologies we rely on today, including cellphones and GPS receivers.

Building on the accomplishments of previous researchers, Harold Lyons and his colleagues at the U.S. National Bureau of Standards (now the National Institute of Standards and Technology), in Washington, D.C., began working in 1947 on developing an atomic clock and demonstrated it to the public two years later. Its design was based on atomic physics. The clock kept time by tracking the microwave signals that electrons in atoms emit when they change energy levels.

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The Transistor at 75

The past, present, and future of the modern world’s most important invention

2 min read
A photo of a birthday cake with 75 written on it.
Lisa Sheehan
LightGreen

Seventy-five years is a long time. It’s so long that most of us don’t remember a time before the transistor, and long enough for many engineers to have devoted entire careers to its use and development. In honor of this most important of technological achievements, this issue’s package of articles explores the transistor’s historical journey and potential future.

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