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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. International Atomic Time - Wikipedia

    en.wikipedia.org/wiki/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 worldwide. [3]

  4. Atomic clock - Wikipedia

    en.wikipedia.org/wiki/Atomic_clock

    GPS Time (GPST) is a continuous time scale and theoretically accurate to about 14 nanoseconds. [107] However, most receivers lose accuracy in the interpretation of the signals and are only accurate to 100 nanoseconds. [108] [109] GPST is related to but differs from TAI (International Atomic Time) and UTC (Coordinated Universal Time).

  5. ΔT (timekeeping) - Wikipedia

    en.wikipedia.org/wiki/ΔT_(timekeeping)

    TT-UT1 2000+ ΔT vs. time from 1657 to 2022 [1] [2] In precise timekeeping, ΔT (Delta T, delta-T, deltaT, or DT) is a measure of the cumulative effect of the departure of the Earth's rotation period from the fixed-length day of International Atomic Time (86,400 seconds).

  6. 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 ...

  7. List of atomic clocks - Wikipedia

    en.wikipedia.org/wiki/List_of_atomic_clocks

    This page was last edited on 6 December 2024, at 01:21 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may apply.

  8. Time in physics - Wikipedia

    en.wikipedia.org/wiki/Time_in_physics

    In the International System of Units (SI), the unit of time is the second (symbol: s). It has been defined since 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", and is an SI base unit. [12]

  9. Time scale - Wikipedia

    en.wikipedia.org/wiki/Time_scale

    Time scale may refer to: Time standard, a specification of either the rate at which time passes, points in time, or both; A duration or quantity of time: Orders of magnitude (time) as a power of 10 in seconds; A specific unit of time; Geological time scale, a scale that divides up the history of Earth into scientifically meaningful periods