Method should allow them to redefine the kilo

are working out how many atoms are in a certain sphere

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.

THE OFFICIAL KILOGRAM AND ITS GRADUAL WEIGHT LOSS 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. Advertisement

‘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.