second
Sign in to saveThe second (symbol: s) is a unit of time derived from the division of the day, first into hours, then into minutes, and lastly into seconds, for a total of 24 × 60 × 60 = seconds per day. That definition, based on of a rotation of the Earth, is still used by the Universal Time 1 (UT1) system.
AI overview
A second is a unit of time that results from dividing a day into progressively smaller units—first into 24 hours, then into 60 minutes, and finally into 60 seconds each, giving 86,400 seconds per day. This measurement system, originally based on Earth's rotation, remains the foundation of the Universal Time 1 (UT1) timekeeping system used today.
AI-generated from the Wikipedia summary — may contain errors.
Key facts
- Unit.name
- second
- Unit.image
- File:Clock-pendulum.gif
- Unit.caption
- A pendulum-governed escapement of a clock, ticking every second
- Unit.standard
- SI
- Unit.quantity
- time
- Unit.symbol
- s
via Wikipedia infobox
Article
21 sectionsContents
- Etymology
- Uses
- Clocks and solar time
- Events and units of time in seconds
- Other units incorporating seconds
- Timekeeping standards
- Optical lattice clock
- History of definition
- Sexagesimal divisions of calendar time and day
- Fraction of solar day
- Fraction of an ephemeris year
- Atomic definition
- Table
- Future redefinition
- Rydberg constant
- Requirements
- SI multiples
- See also
- Notes
- References
- External links
The second (symbol: s) is a unit of time derived from the division of the day, first into hours, then into minutes, and lastly into seconds, for a total of 24 × 60 × 60 = seconds per day. That definition, based on of a rotation of the Earth, is still used by the Universal Time 1 (UT1) system.
The current and formal definition in the International System of Units (SI) is more precise:The second [...] is defined by taking the fixed numerical value of the caesium (Cs) frequency, ΔνCs, the unperturbed ground-state hyperfine transition frequency of the Cs-133 atom, to be when expressed in the unit hertz, which is equal to s−1.