The unit of time: Present and future directions

Publication date: Available online 26 February 2019Source: Comptes Rendus PhysiqueAuthor(s): Sébastien BizeAbstractSome 50 years ago, physicists, and after them the entire world, started to found their time reference on atomic properties instead of motions of the Earth that have been in use since the origin. Far from being an arrival point, this decision marked the beginning of an adventure characterized by an improvement by 6 orders of magnitude in the uncertainty of realization of atomic frequency and time references. Ever-progressing atomic frequency standards and time references derived from them are key resources for science and for society. We will describe how the unit of time is realized with a fractional accuracy approaching 10−16 and how it is delivered to users via the elaboration of the international atomic time. We will describe the tremendous progress of optical frequency metrology over the last 20 years that led to a novel generation of optical frequency standards with fractional uncertainties of 10−18. We will describe work toward a possible redefinition of the SI second based on such standards. We will describe existing and emerging applications of atomic frequency standards in science.RésuméIl y a une cinquantaine d'années, les physiciens, et après eux le monde entier, ont commencé à fonder leur référence temporelle sur les propriétés atomiques au lieu des mouvements de la Terre, qui étaient utilisés depuis l'origine. Loin d'être un point d...

Source: Comptes Rendus Physique - February 27, 2019 Category: Physics Source Type: research