Definitions of Some Base Units
• The metre (m) is the length equivalent to 1650763.73 wavelengths in vacuum of radiation analogous to the transition among the 2p10 and 5d5 levels of the Krypton-86 atom.
• The kilogram (kg) is the standard unit of mass; it is equivalent to the mass of the international prototype of kilogram that is a specific cylinder of platinum-iridium alloy that is preserved in a vault in Sevres, France by the International Bureau of Weights & Measures.
• The second (s) is the duration of 9192631770 periods of the radiation equivalent to the transition among the two hyperfine levels of the ground state of the cesium-133 atom.
• The Kelvin (K), is the unit of thermodynamic temperature, is the fraction i.e., 1/273.16 of thermodynamic temperature of the triple point of water.