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  2. Light-second - Wikipedia

    en.wikipedia.org/wiki/Light-second

    The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics.It is defined as the distance that light travels in free space in one second, and is equal to exactly 299 792 458 m (approximately 983 571 055 ft or 186 282 miles).

  3. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    One trillionth of a second. nanosecond: 10 −9 s: One billionth of a second. Time for molecules to fluoresce. shake: 10 −8 s: 10 nanoseconds, also a casual term for a short period of time. microsecond: 10 −6 s: One millionth of a second. Symbol is μs millisecond: 10 −3 s: One thousandth of a second. Shortest time unit used on ...

  4. Day - Wikipedia

    en.wikipedia.org/wiki/Day

    A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours (86,400 seconds). As a day passes at a given location it experiences morning, noon, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes.

  5. 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 ...

  6. Jiffy (time) - Wikipedia

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

    In astrophysics and quantum physics a jiffy is, as defined by Edward R. Harrison, [13] the time it takes for light to travel one fermi, which is approximately the size of a nucleon. One fermi is 10 −15 m, so a jiffy is about 3 × 10 −24 s. It has also more informally been defined as "one light-foot", which is equal to approximately one ...

  7. Time - Wikipedia

    en.wikipedia.org/wiki/Time

    A minute (min) is 60 seconds in length (or, rarely, 59 or 61 seconds when leap seconds are employed), and an hour is 60 minutes or 3600 seconds in length. A day is usually 24 hours or 86,400 seconds in length; however, the duration of a calendar day can vary due to Daylight saving time and Leap seconds.

  8. SI base unit - Wikipedia

    en.wikipedia.org/wiki/SI_base_unit

    The day is divided into 24 hours, each hour divided into 60 minutes, each minute divided into 60 seconds. A second is 1 / (24 × 60 × 60) of the day. Historically, a day was defined as the mean solar day; i.e., the average time between two successive occurrences of local apparent solar noon. T metre: m length

  9. Planck units - Wikipedia

    en.wikipedia.org/wiki/Planck_units

    One example is represented by the conditions in the first 10 −43 seconds of our universe after the Big Bang, approximately 13.8 billion years ago. The four universal constants that, by definition, have a numeric value 1 when expressed in these units are: c, the speed of light in vacuum, G, the gravitational constant, ħ, the reduced Planck ...