Metre
Query URLs
https://term.museum-digital.de/md-de/tag/41130
- Note
- The metre (or meter in American spelling; symbol: m) is the base unit of length in the International System of Units (SI).
The metre was originally defined in 1791 as one ten-millionth of the distance from the equator to the North Pole along a great circle, so the Earth´s circumference is approximately 40000 km. In 1799, the metre was redefined in terms of a prototype metre bar. The actual bar used was changed in 1889. In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton-86.
The current definition was adopted in 1983 and modified slightly in 2002 to clarify that the metre is a measure of proper length. From 1983 until 2019, the metre was formally defined as the length of the path travelled by light in a vacuum in 1/299792458 of a second. After the 2019 redefinition of the SI base units, this definition was rephrased to include the definition of a second in terms of the caesium frequency ΔνCs.
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Mikrometer zur Bestimmung von Pappendicken
Das kleine Mikrometer wurde...
Object information
Image: Heimatwelten Zwönitz - CC BY-NC-SA -
Dickenmesser Nr. 220 der Firma Louis Schopper
Die schwarze Schachtel...
Object information
Image: Heimatwelten Zwönitz - CC BY-NC-SA
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