Gibney 2017 Nature

Gibney E (2017) New definitions of scientific units are on the horizon. Nature 550:312–13.

» PMID: 29052643 Open Access

Gibney E (2017) Nature

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.

• Bioblast editor: Gnaiger E

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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]