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  2. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    A minute of arc is ⁠π 10 800⁠ of a radian . A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol ″, [2] is ⁠ 1 60 ⁠ of an arcminute, ⁠ 1 3600⁠ of a degree, [1] ⁠ 1 1 296 000⁠ of a turn, and ⁠π 648 000⁠ (about ⁠ 1 206 264.8⁠) of a radian. These units originated in Babylonian astronomy as ...

  3. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    The TU (for time unit) is a unit of time defined as 1024 μs for use in engineering. The Svedberg is a time unit used for sedimentation rates (usually of proteins). It is defined as 10 −13 seconds (100 fs). The galactic year, based on the rotation of the galaxy and usually measured in million years.

  4. Minute - Wikipedia

    en.wikipedia.org/wiki/Minute

    Minute. A digital clock showing zero hours and one minute. Minute is a unit of time defined as equal to 60 seconds. [1] One hour contains 60 minutes. [2] Although not a unit in the International System of Units (SI), the minute is accepted for use in the SI. [1] The SI symbol for minutes is min (without a dot).

  5. Second - Wikipedia

    en.wikipedia.org/wiki/Second

    Second. The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as 86400 of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds each (24 × 60 × 60 = 86400).

  6. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    The speed of light in vacuum, commonly denoted c, is a universal physical constant that is exactly equal to 299,792,458 metres per second (approximately 300,000 kilometres per second; 186,000 miles per second; 671 million miles per hour). [Note 3] According to the special theory of relativity, c is the upper limit for the speed at which ...

  7. Clock angle problem - Wikipedia

    en.wikipedia.org/wiki/Clock_angle_problem

    Clock angle problems relate two different measurements: angles and time. The angle is typically measured in degrees from the mark of number 12 clockwise. The time is usually based on a 12-hour clock . A method to solve such problems is to consider the rate of change of the angle in degrees per minute. The hour hand of a normal 12-hour analogue ...

  8. Time dilation - Wikipedia

    en.wikipedia.org/wiki/Time_dilation

    Time dilation is the difference in elapsed time as measured by two clocks, either because of a relative velocity between them ( special relativity ), or a difference in gravitational potential between their locations ( general relativity ). When unspecified, "time dilation" usually refers to the effect due to velocity.

  9. Light-second - Wikipedia

    en.wikipedia.org/wiki/Light-second

    186 282 mi. 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 mi ). Just as the second forms the basis for other units of time, the ...