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  2. Caesium standard - Wikipedia

    en.wikipedia.org/wiki/Caesium_standard

    The first set of units defined using the caesium standard were those relating to time, with the second being defined in 1967 as "the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom" meaning that: 1 second, s, = 9,192,631,770 Δt Cs

  3. NIST-F2 - Wikipedia

    en.wikipedia.org/wiki/NIST-F2

    NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 cesium fountain atomic clock, a civilian time standard for the United States. NIST-F2 is a caesium fountain atomic clock that, along with NIST-F1, serves as the United States' primary time and frequency standard. [1] NIST-F2 was brought online on 3 April 2014. [1] [2]

  4. Galactic year - Wikipedia

    en.wikipedia.org/wiki/Galactic_year

    The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy. [1] One galactic year is approximately 225 million Earth years. [2]

  5. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    The Jiffy is the amount of time light takes to travel one femtometre (about the diameter of a nucleon). The Planck time is the time that light takes to travel one Planck length. The TU (for time unit) is a unit of time defined as 1024 μs for use in engineering. The svedberg is a time unit used for sedimentation rates (usually

  6. Atomic clock - Wikipedia

    en.wikipedia.org/wiki/Atomic_clock

    where is the spectroscopic linewidth of the clock system, is the number of atoms or ions used in a single measurement, is the time required for one cycle, and is the averaging period. This means instability is smaller when the linewidth Δ ν {\displaystyle \Delta \nu } is smaller and when N {\displaystyle {\sqrt {N}}} (the signal to noise ...

  7. Hafele–Keating experiment - Wikipedia

    en.wikipedia.org/wiki/Hafele–Keating_experiment

    The time difference was measured by direct clock comparison at the ground before and after the flight, as well as during the flight by laser pulses of 0.1 ns duration. Those signals were sent to the plane, reflected, and again received at the ground station. The time difference was observable during the flight, before later analysis.

  8. List of sundial mottos - Wikipedia

    en.wikipedia.org/wiki/List_of_sundial_mottos

    Hours fly, Flowers die. New days, New ways, Pass by. Love stays. [2] Hours fly, Flowers bloom and die. Old days, Old ways pass. Love stays. I only tell of sunny hours. I count only sunny hours. The clouds shall pass and the sun will shine on us once more. Let others tell of storms and showers, I tell of sunny morning hours.

  9. YouTube Kids - Wikipedia

    en.wikipedia.org/wiki/YouTube_Kids

    The YouTube Kids app features parental control settings that allow parents to limit screen time, and restrict users from accessing the search tool. Parents can use a passcode or their Google account to protect these settings, and configure profiles for multiple users to tailor their experiences.