3 articles for "Universal Time"

**Universal Time UT**[Astro*Index]

Essentially equivalent to the now obsolete term GMT (Greenwich Mean Time), although distinct from it in rather subtle ways. It comes in several flavors: UT0, UT1, UT2, and UTC.

See also:

♦ Greenwich Mean Time

**Universal Time UT**[Munkasey M.]

The clock time as kept at the zero or Greenwich meridian. UT in principle is determined by the average rate of the Sun's apparent diurnal motion relative to the Greenwich meridian. However, the numerical measure of UT at any instant is computed from observations of the motions of the planets. UT is the basis for all civil or clock timekeeping.

**UT0** – The same as: "Universal Time".

**UT1** – This is Universal Time (or UTO) corrected for the observed motion ofthe Earth's geographic poles or of the speeding up or slowing down in the rate of rotation of the Earth. UT1 is computed from an astronomical observational basis.

**UT2** – Time corrected for the mean seasonal variations in the rate ofrotation of the Earth.

See also:

♦ Greenwich Mean Time

**Universal Coordinated Time UTC**[Astro*Index]

The stepped time kept by most time broadcasting stations which is determined by atomic clocks. UTC is derived from TAI (*International Atomic Time*)

See also:

♦ International Atomic Time

**Universal Coordinated Time UTC**[Munkasey M.]

Coordinated Universal Time: The stepped time kept by most timebroadcasting stations which is determined by atomic clocks. The length of the second which is used in atomic clocks is measured through counting the vibrations of a Cesium beam oscillator and not through astronomical means.

See also:

♦ International Atomic Time

Astro*Index Copyright © 1997 Michael Erlewine