Gibney 2017 Nature
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Gibney E (2017) New definitions of scientific units are on the horizon. Nature 550:312–13. |
Abstract: Revamped definitions of scientific units are on their way. In the biggest overhaul of the international system of units (SI) since its inception in 1960, a committee is set to redefine four basic units — the ampere, the kilogram, the kelvin and the mole — using relationships to fundamental constants, rather than abstract or arbitrary definitions. The International Bureau of Weights and Measures is reviewing the plans at a meeting near Paris from 16 to 20 October. Its recommendations will then go before the General Conference on Weights and Measures, which oversees the SI system, in November 2018. The changes would take effect in May 2019.
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- Entity, count, and number, and SI base quantities / SI base units
Quantity name Symbol Unit name Symbol Comment elementary U_{X} elementary unit [x] U_{X}, U_{B}; [x] not in SI count N_{X} elementary unit [x] N_{X}, N_{B}; [x] not in SI number N - dimensionless = N_{X}·U_{X}^{-1} amount of substance n_{B} mole [mol] n_{X}, n_{B} electric current I ampere [A] A = C·s^{-1} time t second [s] length l meter [m] SI: metre mass m kilogram [kg] thermodynamic temperature T kelvin [K] luminous intensity I_{V} candela [cd]
- Fundamental relationships
- » Avogadro constant N_{A}
- » Boltzmann constant k
- » elementary charge e
- » Faraday constant F
- » gas constant R
- » electrochemical constant f
- Fundamental relationships
- SI and related concepts
Further reading
- Gibney E (2018) Largest overhaul of scientific units since 1875 wins approval. Nature 563:451–2. - nature.com
- Bureau International des Poids et Mesures (2019) The International System of Units (SI). 9th edition:117-216 ISBN 978-92-822-2272-0. - »Open Access pdf«
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Avogadro constant