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  2. Atomic clock - Wikipedia

    en.wikipedia.org/wiki/Atomic_clock

    Atomic clocks are installed at sites of time signal radio transmitters. [103] They are used at some long-wave and medium-wave broadcasting stations to deliver a very precise carrier frequency. [104] Atomic clocks are used in many scientific disciplines, such as for long-baseline interferometry in radio astronomy. [105]

  3. WWVB - Wikipedia

    en.wikipedia.org/wiki/WWVB

    WWVB's Colorado location makes the signal weakest on the U.S. east coast, where urban density also produces considerable interference. In 2009, NIST raised the possibility of adding a second time code transmitter, on the east coast, to improve signal reception there and provide a certain amount of robustness to the overall system should weather or other causes render one transmitter site ...

  4. History of time in the United States - Wikipedia

    en.wikipedia.org/wiki/History_of_time_in_the...

    The evolution of United States standard time zone boundaries from 1919 to 2024 in five-year increments. Plaque in Chicago marking the creation of the four time zones of the continental US in 1883 Colorized 1913 time zone map of the United States, showing boundaries very different from today Map of U.S. time zones during between April 2, 2006, and March 11, 2007.

  5. NIST-F1 - Wikipedia

    en.wikipedia.org/wiki/NIST-F1

    NIST-F1, source of the official time of the United States. NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the United States' primary time and frequency standard. The clock took fewer than four years to test and build, and was developed ...

  6. NIST-7 - Wikipedia

    en.wikipedia.org/wiki/NIST-7

    It was one of a series of Atomic Clocks [1] at the National Institute of Standards and Technology. Eventually, it achieved an uncertainty of 5 × 10 −15 . The caesium beam clock served as the nation's primary time and frequency standard during that time period, but it has since been replaced with the more accurate NIST-F1 , a caesium fountain ...

  7. Atomic scientists adjust 'Doomsday Clock' closer than ever to ...

    www.aol.com/news/atomic-scientists-adjust...

    The Bulletin of the Atomic Scientists set the clock to 89 seconds before midnight - the theoretical point of annihilation. That is one second closer than it was set last year.

  8. The 'Doomsday Clock' just moved closer to midnight. Here's ...

    www.aol.com/news/doomsday-clock-just-moved...

    Humanity is closer to destroying itself, according to atomic scientists who revealed on Tuesday that the famous “Doomsday Clock” was set to 89 seconds to midnight — the closest it has ever been.

  9. List of time periods - Wikipedia

    en.wikipedia.org/wiki/List_of_time_periods

    Early modern period – The chronological limits of this period are open to debate. It emerges from the Late Middle Ages (c. 1500), demarcated by historians as beginning with the fall of Constantinople in 1453, in forms such as the Italian Renaissance in the West, the Ming dynasty in the East, and the rise of the Aztecs in the New World.