Concept information
优选词，正式主题词
SECseconde
定义
- The $Second$ (symbol: $s$) is the base unit of time in the International System of Units (SI) and is also a unit of time in other systems of measurement. Between the years1000 (when al-Biruni used seconds) and 1960 the second was defined as $1/86400$ of a mean solar day (that definition still applies in some astronomical and legal contexts). Between 1960 and 1967, it was defined in terms of the period of the Earth's orbit around the Sun in 1900, but it is now defined more precisely in atomic terms. Under the International System of Units (via the International Committee for Weights and Measures, or CIPM), since 1967 the second has been defined as the duration of ${9192631770}$ periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.In 1997 CIPM added that the periods would be defined for a caesium atom at rest, and approaching the theoretical temperature of absolute zero, and in 1999, it included corrections from ambient radiation.
上位概念
狭义概念
- as Attosecond (en)
- J74 Centipoise per Bar (en)
- L95 Common Year (en)
- DAY Day (en)
- C26 decisecond (en)
- fs Femtosecond (en)
- H03 Henry per Kiloohm (en)
- H04 Henry per Ohm (en)
- HUR Hour (en)
- B52 kilosecond (en)
- 1000 a KiloYear (en)
- mo_g Mean Gregorian Month (en)
- mo_j Mean Julian Month (en)
- Ms megasecond (en)
- y (metrology) metrology year (en)
- G98 Microhenry per Kiloohm (en)
- G99 Microhenry per Ohm (en)
- B98 microsecond (en)
- H05 Millihenry per Kiloohm (en)
- H06 Millihenry per Ohm (en)
- Ma Million Years (en)
- L16 Millipascal Second per Bar (en)
- ms millisecond (en)
- MIN Minute (en)
- MON Month (en)
- C47 nanosecond (en)
- H07 Pascal Second per Bar (en)
- H70 Picosecond (en)
- tₚ Planck Time (en)
- F06 Poise per Bar (en)
- N35 poise per pascal (en)
- M56 Shake (en)
- day{sidereal} Sidereal Day (en)
- hr{sidereal} Sidereal Hour (en)
- min{sidereal} Sidereal Minute (en)
- L96 Sidereal Year (en)
- mo_s Synodic month (en)
- D42 Tropical Year (en)
- WEE Week (en)
- ANN Year (en)
其它语言
URI
https://vocab.sentier.dev/units/unit/SEC
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