A big step towards the redefinition of the kelvin
Metrologists are measurement artists who are very precise in the case of the Boltzmann constant up to the sixth decimal place. Whoever is able to determine it very exactly will cause a small revolution in the field of worldwide temperature measurement: The temperature unit will then no longer be based - as hitherto - on a chemico-physical material property, i.e. the triple point of water, but on an unchangeable fundamental constant. Scientists of the Physikalisch-Technische Bundesanstalt (PTB) have now succeeded in re-determining the Boltzmann constant. Although the uncertainty of the result is not yet sufficient for a redefinition of the kelvin, it furnishes proof that the procedure selected by PTB is basically a suitable one. The physicists expect that in the next two years they will be able to reduce the uncertainty to such an extent that a redefinition of the kelvin will be possible. These results have been...