Editing Torr (section)

==History==
Torricelli attracted considerable attention when he demonstrated the first [[Barometer#Mercury barometers|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 enabled.

Over time, 760 millimetres of mercury at 0&nbsp;°C 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 at 0&nbsp;°C. However, since the acceleration due to gravity – and thus the weight of a column of mercury – is a function of elevation and latitude (due to the rotation and non-[[sphericity]] of the Earth), this definition is imprecise and varies by location.

In 1954, the definition of the ''atmosphere'' was revised by the [[10th General Conference on Weights and Measures]]<ref>[http://www.bipm.org/en/CGPM/db/10/4/ BIPM – Resolution 4 of the 10th CGPM].</ref> to the currently accepted definition: one atmosphere is equal to 101325 [[pascal (unit)|pascals]]. The torr was then redefined as {{sfrac|760}} of one atmosphere. This yields a precise definition that is unambiguous and independent of measurements of the density of mercury or the acceleration due to gravity on Earth.