Hertz Hz
About the Hertz
The hertz is one cycle or event per second and replaced the older expression cycles per second. It is named after Heinrich Hertz, who first demonstrated electromagnetic waves. Mains electricity runs at 50 or 60 Hz, and the caesium frequency that defines the second is 9,192,631,770 Hz.
Related Units
Second
sBase unit; caesium-133 frequency = 9,192,631,770 Hz exactly
The second is defined by taking the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom to...
Day
d1 d = 86,400 s (exact)
As a unit accepted for use with the SI, the day is exactly 86,400 seconds. The actual solar day varies slightly and the...
Julian year
a365.25 d = 31,557,600 s (exact)
In astronomy the Julian year is exactly 365.25 days of 86,400 seconds, or 31,557,600 seconds. It is the year used to...
Radian
rad1 rad = 1 m/m (dimensionless); 180°/π
A radian is the angle subtended at the centre of a circle by an arc equal in length to the radius, so a full turn is 2π...