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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:
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 by Steve Jefferts and Dawn Meekhof of the Time and ...
F6CTE's CLOCK [15] WWV: 2.5, 5, 10, 15, and 20 MHz AM Voice with modified IRIG-Hformat time code on 100 Hz sub-carrier (CCIR code) HF radio and antenna (plus software if automatic updating of computer time is desired) TrueTime TL-3 WWV Receiver; ntpd with Radio WWV Audio Demodulator/Decoder (driver can tune ICOM HF radios via C-IV) COAA's Radio ...
The majority of the clocks involved are caesium clocks; the International System of Units (SI) definition of the second is based on caesium. [6] The clocks are compared using GPS signals and two-way satellite time and frequency transfer. [7] Due to the signal averaging TAI is an order of magnitude more stable than its best constituent clock.
NIST-F1, a cesium fountain atomic clock used since 1999, has a fractional inaccuracy (δf / f) of less than 5 × 10 −16. The planned performance of NIST-F2 is δ f / f < 1 × 10 −16 . [ 3 ] At this planned performance level the NIST-F2 clock will not lose a second in at least 300 million years.
A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation.It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies.
The North American Central Time Zone (CT) is a time zone in parts of Canada, the United States, Mexico, Central America, and some Caribbean islands. [1]In parts of that zone (20 states in the US, three provinces or territories in Canada, and several border municipalities in Mexico), the Central Time Zone is affected by two time designations yearly: Central Standard Time (CST) is observed from ...
Nautical time divides the globe into 24 nautical time zones with hourly clock offsets, spaced at 15 degrees by longitudinal coordinate, with no political deviation. Nautical timekeeping dates back to the early 20th century as a standard way to keep time at sea, although it largely only applied to military fleets pre–World War 2.