A prominent German institute has said it plans to redefine the kilogramme, following concerns that the current standard kilo has been shedding weight. Over the next two years researchers at the German National Metrology Institute (PTB) in Braunschweig plan to count the atoms in two pure silicon spheres that are 10-centimetres in diameter. One of the spheres, the most perfect of their kind in the world, arrived in Braunschweig on Friday. The other will go to researchers in Japan."The former reference object is no longer exact enough," said faculty leader Peter Becker on Friday.
The old platinum alloy standard kilogramme - the original from 1889 - is housed in vault near Paris, France, and is slowly losing weight, though it's barely measurable, Becker said. Scientists aren't sure why.
PTB researchers will count atoms in the new silicon spheres with the highest possible accuracy to create an equation for a new definition of the kilogramme.
The five-year assembly took place in St. Petersburg, Berlin, and the Russian city of Nizhny Novgorod and cost a total of €2 million.
Becker said time is short to finish the project, because researchers in Switzerland and Britain are currently using other methods to solve the same problem. "Of course we hope that our definition of the kilogramme succeeds," he said. "But the final decision is up to the politicians."
But the new formula, regardless of which team succeeds in establishing a new kilogramme definition, won't have a commonplace purpose. "Our work serves precise measurements," Becker said. "No one should fear that the contents of their shopping bags will suddenly be heavier."