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  2. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    The amount of time light takes to travel one fermi (about the size of a nucleon) in a vacuum. zeptosecond: 10 −21 s: One sextillionth of a second. Time measurement scale of the NIST and JILA strontium atomic clock. Smallest fragment of time currently measurable is 247 zeptoseconds. [3] attosecond: 10 −18 s: One quintillionth of a second ...

  3. Orders of magnitude (time) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(time)

    The smallest meaningful increment of time is the Planck time―the time light takes to traverse the Planck distance, many decimal orders of magnitude smaller than a second. [ 1 ] The largest realized amount of time, based on known scientific data, is the age of the universe , about 13.8 billion years—the time since the Big Bang as measured in ...

  4. List of radioactive nuclides by half-life - Wikipedia

    en.wikipedia.org/wiki/List_of_radioactive...

    Twenty-three yoctoseconds is the time needed to traverse a 7-femtometre distance at the speed of light—around the diameter of a large atomic nucleus. 10 −21 seconds (zeptoseconds) [ edit ]

  5. Doomsday Clock - Wikipedia

    en.wikipedia.org/wiki/Doomsday_Clock

    The farthest time from midnight was 17 minutes in 1991, and the nearest is 89 seconds, set in January 2025. [ 5 ] The Clock was moved to 150 seconds (2 minutes, 30 seconds) in 2017, then forward to 2 minutes to midnight in 2018, and left unchanged in 2019. [ 6 ]

  6. Attosecond - Wikipedia

    en.wikipedia.org/wiki/Attosecond

    An attosecond (abbreviated as as) is a unit of time in the International System of Units (SI) equal to 10 −18 or 1 ⁄ 1 000 000 000 000 000 000 (one quintillionth) of a second. [ 1 ] An attosecond is to a second, as a second is to approximately 31.69 billion years.

  7. Standard frequency and time signal service - Wikipedia

    en.wikipedia.org/wiki/Standard_frequency_and...

    Standard frequency and time signal service (short: SFTS) is, according to Article 1.53 of the International Telecommunication Union's (ITU) Radio Regulations (RR), [1] "A radiocommunication service for scientific, technical and other purposes, providing the transmission of specified frequencies, time signals, or both, of stated high precision, intended for general reception".

  8. Military time zone - Wikipedia

    en.wikipedia.org/wiki/Military_time_zone

    The military time zones are a standardized, uniform set of time zones for expressing time across different regions of the world, named after the NATO phonetic alphabet. The Zulu time zone (Z) is equivalent to Coordinated Universal Time (UTC) and is often referred to as the military time zone.

  9. 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