Universal Time
by Vinutha[ Edit ] 2010-02-12 12:24:21
Universal Time (UT) is the precise, internationally accepted measure of time, used for all civil timekeeping and scientific work. Universal Time is measured by an atomic clock. Its basic unit is the atomic second the length of time in which 9,192,631,770 oscillations (vibrations) are emitted by a radioactive cesium atom.
On January 1, 1972, UT went into effect, replacing Greenwich Mean Time (GMT). In GMT, a day was measured as the time between successive passages of the sun over Greenwich, England. Greenwich is the location of the prime meridian, the meridian of 0 degrees longitude, used as a point of reference for positions east and west on the globe.
One advantage of UT over GMT is that it is a more accurate time-keeping system. Another advantage of UT is that time can be readily determined without making astronomical observations.
