History
Torricelli attracted considerable attention when he demonstrated the first mercury barometer to the general public. He is credited with giving the first modern explanation of atmospheric pressure. Scientists at the time were familiar with small fluctuations in height that occurred in barometers. When these fluctuations were explained as a manifestation of changes in atmospheric pressure, the science of meteorology was born.
Over time, 760 millimetres of mercury came to be regarded as the standard atmospheric pressure. In honour of Torricelli, the Torr was defined as a unit of pressure equal to one millimetre of mercury.
In 1954, the definition of the atmosphere was revised by the 10e Conférence Générale des Poids et Mesures (10th CGPM) to the currently accepted definition: one atmosphere is equal to 101325 pascals. The torr was then redefined as 1⁄760 of one atmosphere. This was necessary in place of the definition of the torr as one millimetre of mercury, because the height of mercury changes at different temperatures and gravities.
Read more about this topic: Torr
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