BASE QUANTITIES

Ever wondered what exactly metre/meter or second means?
Here you'll find all the basic fundamental quantities along with their definition.

1. Meter (m) It is the length of the path travelled by light in vacuum during the time interval of 1/299,792,458 of a second. (1983)
   
   
   
2. Kilogram (kg) The kilogram is equal to the mass of the international prototype of the kilogram (a platinum-iridium alloy cylinder) kept at International Bureau of Weights and Measures, at Sevres, France. (1889)
   
   
   
3. Second (s) The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the 2 hyperfine levels of the ground state of Cesium-133 atom. (1967)
   
   
   
4. Ampere (A) It is that constant of current which, if maintained in 2 straight parallel conductors of infinite length, of negligible cross section and placed 1m apart in vacuum, would produce between these conductors a force equal to 2 x 10^-7 Newton per meter of length. (1948)
   
   
   
5. Kelvin (K) It is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. (1967)
   
   
   
6. Mole (mol) The mole is the amount of substance of a system, which contains as many elementary entities as there are atoms in 0.012 kilogram of Carbon-12 (1971)
   
   
   
7. Candela (Cd) It is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. (1979)