The International Prototype Kilogram ( pictured ) shed 0.0001g last century , leading scientists to come up with a more accurate measure of mass . It ’ s a problem that has been weighing on scientists ’ minds for years – how to redefine and accurately measure the kilogram . Currently the unit of measurement is based on a metal cylinder - which should weigh precisely 1,000 grams - that is kept under lock and key in Paris . But the cylinder is gradually losing mass , leading German researchers to look for a new formula to create the most accurate definition of a kilo . The International Prototype Kilogram shed 100 micrograms ( 0.0001g ) last century , which although is around the weight of dust particle , means the official kilogram is becoming slowly less accurate . Scientists at the German Nation Metrology Institute ( PTB ) in Braunschweig have come up with an ingenious way to create a more exact measure of mass , which involves counting the number of atoms needed to make up a kilogram , instead of relying on a piece of metal . But in order to win the international race to redefine the kilogram , they must perfect the method by developing the world ’ s roundest sphere . Horst Bettin , head of the PTB 's kilogram project , said : 'Our goal is to have PTB master the realisation of the future kilogram completely anonymously. ’ After years of research , they have created a method of making incredibly pure circular crystals made from tiny vortices of silicon gas . From incredibly pure silicon , they are able to grow a flawless single-crystal whose inner structure is completely regular and without fractures . The company said : 'Both being free of impurities and having a regular structure are preconditions for the success of the experiment . ' 'From the round-bodied , cylindrical single-crystals , PTB produces crystal spheres that are rounder than anything else in the world. ’ Scientists at the German Nation Metrology Institute ( PTB ) in Braunschweig have come up with an ingenious way to create a more exact measure of mass , but they first need to perfect their technique by counting the atoms in the world 's rounded spheres ( pictured ) The aim is ‘ to produce the connection between the mass of the sphere and the mass of an atom , ' by counting the atoms . Physicist Peter Becker told The Local : ‘ We work out the number of atoms in the sphere , weigh the sphere and therefore work out how much an atom weighs. ’ This mathematical method has enabled the mathematicians to discover the Avogadro constant . The company said : 'Already at this point , PTB scientists miscount only twice every one hundred million atoms . Kilograms of different materials are based on the measurement of the International Prototype Kilogram ( IPK ) . ‘ The kilogram is the unit of mass ; it is equal to the mass of the international prototype of the kilogram , ’ according to Bureau International des Poids et Mesures ( BIPM ) . The cylinder , which is meant to weigh exactly a kilogram , has a diameter of 3.9cm . The cylinder , which is meant to weigh exactly a kilogram , has a diameter of 3.9cm . It ’ s made from an alloy that is 90 per cent platinum and 10 per cent iridium . An illustration of the cyclinder is shown . It ’ s made from an alloy that is 90 per cent platinum and 10 per cent iridium . It ’ s been looked after in Paris by the BIPM since 1889 and replacements have been made to maintain its accuracy . The unit of mass is disseminated throughout the world via ‘ official copies ’ . ‘ With these copies and via further transfer standards , we teach weighing instruments how heavy a kilogram is , ’ PTB scientists explained . But the official IPK has shed 100 micrograms ( 0.0001g ) in the last century , prompting experts to find a more exact way of defining the kilogram . ‘ At worst , the international prototype of the kilogram could be destroyed or stolen all of a sudden [ if an alternative isn ’ t created ] . Then the definition would be lost for all time , ’ the PTB said . ‘ The goal is to miscount only by one atom for every one hundred million atoms. ’ The method could be used to work out how many atoms are needed to make up a kilogram , but leaves the challenge of counting how many atoms make up an object . In the case of the sphere , it is possible because the 3D shape is composed of a regular crystal lattice . The researchers who created the sphere know the dimensions of the sphere and the individual layers of lattices , so they are able to calculate the number of atoms by dividing the larger dimension by the smaller one . They believe they will have the answer in 2018 .
International Prototype Kilogram shed 100 years last century . atomic measurement is set from the highly - guarded metal detector . German scientists are figuring out how many atoms are in a certain sphere . Method methods allow them to redefine the kilo based on the number of atoms .