Regensburg 2019 – wissenschaftliches Programm
PLV I: Plenarvortrag
Montag, 1. April 2019, 08:30–09:15, H1
Linking the International System of Units to Fundamental Constants — •Joachim Ullrich — Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Brauschweig, Germany
In November 2018, the General Conference for Weights and Measures, CGPM, established by the Metre Convention in 1875, decided on the revision of the International System of Units (SI). The signatory states of the Metre Convention represent about 98 % of the world's economic power and, thus, the SI is the very foundation of global, international trade and the reliability of measurements worldwide. As suggested by Max Planck when postulating the "Planck constant" in 1900, the revised SI shall be based on fixing the numerical values of "defining constants": the velocity of light, the elementary charge, the Boltzmann, Avogadro and the Planck constants, the Cs hyperfine clock transition and the luminous efficacy. The revision is based on our present theoretical understanding of the microscopic world and is meant to ensure that the units are valid and realizable "for all times and civilizations, throughout the Universe" as envisioned by Max Planck. The talk will give an overview on the revised SI and its advantages as compared to the previous definitions, focusing in particular on future perspectives for innovative technologies. The question of whether the "defining fundamental constants" are indeed constant in time and the topic of next generation clocks will be addressed briefly.