second
Non-SI unit accepted for use with SI
Name | Symbol | Quantity | Value in SI units | |
second | ″ | plane angle, phase angle |
^{π}⁄_{648 000} rad | |
DefinitionThe arc second, symbol ″, is a non-SI unit of plane angle accepted for use with the SI. |
The arc second is a non-SI unit accepted for use with the SI.
The conversion between radians and arc seconds follows from the relations: 1 turn = 360°, 1° = 60′ and 1′ = 60″.
For some applications such as in astronomy, small angles are measured in arcseconds (i.e. seconds of plane angle), denoted as ″, or milliarcseconds, microarcseconds and picoarcseconds, denoted mas, μas and pas, respectively, where arcsecond is an alternative name for second of plane angle.