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  2. Timeline for the day of the September 11 attacks - Wikipedia

    en.wikipedia.org/wiki/Timeline_for_the_day_of...

    10:07: NBC reports for the first time that the South Tower of the World Trade Center has collapsed. Prior to this time they have said only that a section of the building has fallen away. 10:07: NEADS, controlling the only set of fighters over Washington, first learns of the hijacking of Flight 93, 4 minutes after it actually crashed.

  3. WWVB - Wikipedia

    en.wikipedia.org/wiki/WWVB

    WWVB is a time signal radio station near Fort Collins, Colorado and is operated by the National Institute of Standards and Technology (NIST). [1] Most radio-controlled clocks in North America [2] use WWVB's transmissions to set the correct time. The normal signal transmitted from WWVB is 70 kW ERP and uses a 60 kHz carrier wave yielding a ...

  4. WWV (radio station) - Wikipedia

    en.wikipedia.org/wiki/WWV_(radio_station)

    WWV is a shortwave ("high frequency" or HF) radio station, located near Fort Collins, Colorado. It has broadcast a continuous time signal since 1945, and implements United States government frequency standards, with transmitters operating on 2.5, 5, 10, 15, and 20 MHz. [1] WWV is operated by the U.S. National Institute of Standards and ...

  5. Speaking clock - Wikipedia

    en.wikipedia.org/wiki/Speaking_clock

    Speaking clock. A speaking clock or talking clock is a live or recorded human voice service, usually accessed by telephone, that gives the correct time. The first telephone speaking clock service was introduced in France, in association with the Paris Observatory, on 14 February 1933.

  6. Coordinated Universal Time - Wikipedia

    en.wikipedia.org/wiki/Coordinated_Universal_Time

    This is an accepted version of this page This is the latest accepted revision, reviewed on 19 September 2024. Primary time standard "UTC" redirects here. For the time zone between UTC−1 and UTC+1, see UTC+00:00. For other uses, see UTC (disambiguation). Current time zones Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a ...

  7. International Atomic Time - Wikipedia

    en.wikipedia.org/wiki/International_Atomic_Time

    International Atomic Time. International Atomic Time (abbreviated TAI, from its French name temps atomique international[1]) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid. [2] TAI is a weighted average of the time kept by over 450 atomic clocks in over 80 national laboratories ...

  8. Atomic clock - Wikipedia

    en.wikipedia.org/wiki/Atomic_clock

    Louis Essen (right) and Jack Parry (left) standing next to the world's first caesium-133 atomic clock in 1955, at the National Physical Laboratory in west London.. The Scottish physicist James Clerk Maxwell proposed measuring time with the vibrations of light waves in his 1873 Treatise on Electricity and Magnetism: 'A more universal unit of time might be found by taking the periodic time of ...

  9. Radio clock - Wikipedia

    en.wikipedia.org/wiki/Radio_clock

    Radio clock. A modern LF radio-controlled clock. A radio clock or radio-controlled clock (RCC), and often colloquially (and incorrectly [1]) referred to as an "atomic clock", is a type of quartz clock or watch that is automatically synchronized to a time code transmitted by a radio transmitter connected to a time standard such as an atomic clock.