Fundamental constants are essential elements to describe the world: they appear in the physical theories - with the theories themselves being unable to state their values. Therefore, these constants must be measured experimentally - a basic task of metrology. - CODATA database (NIST) - Introduction to the constants for nonexperts (NIST) - Fundamental constants and the SI (part of the Thematic tour "Guardian of the units") - - Values of important constants Fundamental constants – a short introduction © Physikalisch-Technische Bundesanstalt WEB-Redaktion