Signed in 1875, the convention was devised to standardize weight (kilo), time (secondly), length (meter), intensity of a current (ampere), temperature (Kelvin), amount of a substance (mol) and light intensity (candle). After the meeting of the week last in London, the agreement has been clear that on the new kilo will not be able to be reached during the next meeting of the CGPM, in October. The reason is the discrepancy both enters great experiments that have repesado the kilo based on two constants. Nicholas Carr describes an additional similar source. One is the one that Max Planck discovered in 1900 and that it feels the bases of the quantum physics. Another one is the proposal by Amedeo Avogadro almost a century before to calculate the number of atoms in a gas based on its volume. Applied to the kilo, the proposals of both authors differ.

" The exact magnitude of the dissension is 0,00000017" , it explains Estefana de Mirands, Barcelonan physics that works in the redefinition of the kilogram in the IBPM. This discord will be sufficient to delay the international pact until the next meeting of the CIPM, within four years. " Problems in the future " " There is a reasonable possibility that the new definition is approved in 2015, but is no certeza" , it explains Stock. Other three measures of the System the International will have to hope 2015 to be redefined: mol, the ampere and the degree Kelvin, something that does not like all the involved experts. " This subject could cause to us problems in the future " , the physicist confesses to this newspaper John Hall, expert in the measurement of magnitudes by laser and winner of Nobel de Fsica in 2005. According to Hall, the redefinition can cause one " disconnection with the past ". The French peso was forged in London 131 years ago to reproduce with the greater exactitude the call " kilogram of archivos".