IMFUFA-seminar on the question: How long is a metre?
Meet Finn Berg Rasmussen, Niels Bohr Institute, University of Copenhagen who will speak about the question: How long is a metre?
The metric system of units was born in 1799, in the wake of the french revolution. In that year a metre stick and a kilogram weight, both of platinum, were deposited in the french National Archives in Paris. The original aim was to connect the two units to universal constants, but in the interest of accuracy this idea had to be given up, whereafter the metre and the kilogram became defined in terms of the two platinum objects in Paris. SI, the international system of units, took its formal beginning in 1875, when a number of nations signed the International Metre Convention. Since “Metrology Day” 2019 (May 20th) the last of the defining artefacts, the International Prototype Kilogram, IPK, is obsolete, Now the fundamental units of the SI are all defined by assigning numerical values to selected constants of nature such as the charge of the electron or Planck's Constant. In fact only one unit, the second, relies on properties of a particular substance (atoms of the isotope Caesium-133). In some cases the new definitions are easier to understand than the old ones, while the definitions of Kilogram and Kelvin are less obvious.
Seminaret foregår på engelsk.
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