Dobili smo nov kilogram
We have a new kilogram
Written by Dr. Katja Žerjavič, translated by JL Flanner
Pred več kot dvesto leti so meroslovci določili, koliko tehta en kilogram: točno en liter vode.
More than two hundred years ago, metrologists determined how much one kilogram weighs: exactly one litre of water.
Kmalu so ugotovili, da takšno merilo ni najbolj natančno. Izdelali so kilogramski valj iz platine, ki je bolj zanesljivo in priročno merilo. Poimenovali so ga mednarodni prototipni kilogram.
They soon found that such a criterion was not the most accurate. They made a one kilogram platinum cylinder, which is a more reliable and convenient measure. It was called the International Prototype of the Kilogram.
Ta valj je edini predmet na svetu, ki tehta točno en kilogram. Shranjen je pod tremi steklenimi zvonovi v trezorju Mednarodnega biroja za uteži in mere v Parizu.
This cylinder is the only object in the world that weighs exactly one kilogram. It is stored under three glass bells in the vault of the International Bureau of Weights and Measures in Paris.
Naredili so še 67 njegovih kopij, ki so spravljene v laboratorijih po vsem svetu. Občasno jih zmerijo in primerjajo z izvirnikom.
There were also 67 copies made, which are stored in laboratories around the world. Occasionally they are measured and compared with the original.
Odkrili so, da so se mase valja in kopij sčasoma spremenile. To je velik problem za inženirje in znanstvenike, ki morajo meriti izredno natančno.
It was found that the masses of the cylinder and the copies changed over time. This is a major problem for engineers and scientists, who need to measure extremely accurately.
Meroslovci so se zato odločili, da morajo kilogram ponovno določiti, vendar tokrat še bolj natančno.
Metrologists therefore decided to re-determine the kilogram, but this time even more precisely.
Minuli petek so zato na mednarodnem sestanku izglasovali, da od maja prihodnje leto kilogram ne bo več določen s predmetom, ampak z zapleteno fizikalno enačbo.
Last Friday, at an international meeting, they voted that from May next year the kilogram will no longer be determined by an object, but by a complex physical equation.
Kilogram bo seveda še vedno tehtal en kilogram.
A kilogram will, of course, still weigh one kilogram.
»Ponovna določitev je podobna prenovi kleti v hiši. Na koncu je hiša od zunaj videti enako, vendar je zaradi boljših temeljev manj verjetno, da se bo porušila,« je pojasnil Michael de Podesta, raziskovalec iz londonskega nacionalnega laboratorija za fiziko.
"Redefining is similar to renovating the cellar in a house. In the end, the house looks the same from the outside, but it is less likely to collapse due to better foundations, "explains Michael de Podesta, a researcher at the London National Laboratory of Physics.
Znanstveniki bodo v prihodnosti lahko natančno računali maso, pri tem pa jim ne bo treba uporabiti kovinskega valja.
In the future scientists will be able to more accurately calculate mass, but will not need to use a metal cylinder.
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