Hulleye Comes By!

maybe the artsaypunk can define this a bit better, but if anyone ever asks you outside of the sub-continent, you could redirect them here to explain what a desi is.

finally the kilogram is getting a redefinition. it was the only unit left that was not defined by a fundamental constant found in nature, but instead used a physical object as measure. it is currently defined as the mass of a plum sized platinum-iridium alloy which is stored in climate controlled conditions in a vault at Le Bureau International des Poids et Mesures (BIPM) near Paris.

the other six fundamental unit’s of measure are the meter (unit of length) which is defined as the length of the path traveled by light in an absolute vacuum during a time interval of exactly 1/299,792,458 of a second.

the other six units are defined below by natural constants and have moved from being defined by physical objects:

the second (unit of time) is defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom at zero kelvins.

the ampere (unit of electric current) is defined as the constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed one metre apart in vacuum, would produce between these conductors a force equal to 2 10−7 newton per metre of length.

the kelvin (unit of temperature) defined by two facts: zero kelvins is absolute zero (when molecular motion stops), and one kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The Celsius temperature scale is now defined in terms of the kelvin, with 0 C corresponding to 273.15 kelvins, approximately the melting point of water under ordinary conditions.

the mole (unit of substance) is the amount of substance of a system and is defined as the amount of substance that contains as many elementary entities as there are atoms in exactly 0.012 kilogram of carbon-12. This quantity is known as Avogadro’s number and is approximately 6.0221415 × 10²³.

the last unit, the candela (unit of luminosity), formerly known as the candle, is defined as the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 Hz and that has a radiant intensity in that direction of (1/683) W per steradian.

for further definitions, go here. intriguingly, this is the history behind the kilogram.

browse through the bipm website to understand why we cannot use physical subtances to measure basic units anymore. it’s quite fun if you’re at all scientifically inclined.