Proposal Proposed redefinition of SI base units

the bipm s consultative committee units (ccu) proposed that, in addition speed of light, 4 further constants of nature should defined have exact values. using codata 2017 values, these be:

the planck constant h 6966662607015000000♠6.62607015×10 joule-second (j⋅s).
the elementary charge e 6981160217663400000♠1.602176634×10 coulomb (c).
the boltzmann constant k 6977138064900000000♠1.380649×10 joule per kelvin (j⋅k).
the avogadro constant na 7023602214076000000♠6.02214076×10 reciprocal mole (mol).

these constants described in 2006 version of si manual, in version latter 3 defined constants obtained experiment rather defining constants .

the ccu proposed numerical values associated following constants of nature retained unchanged:

the speed of light c 7008299792458000000♠299792458 metres per second (m⋅s).
the ground state hyperfine splitting frequency of caesium-133 atom Δν(cs)hfs 7009919263177000000♠9192631770 hertz (hz).
the luminous efficacy kcd of monochromatic radiation of frequency 7014540000000000000♠540×10 hz 7002683000000000000♠683 lumen per watt (lm⋅w).

the 7 definitions above rewritten below after converting derived units (joule, coulomb, hertz, lumen , watt) 7 base units (second, metre, kilogram, ampere, kelvin, mole , candela), according updated draft of 9th edition of si brochure (2016). in list follows, symbol sr stands dimensionless unit steradian.

Δνcs = Δν(cs)hfs = 7009919263177000000♠9192631770 s
c = 7008299792458000000♠299792458 m⋅s
h = 6966662607015000000♠6.62607015×10 kg⋅m⋅s
e = 6981160217663400000♠1.602176634×10 a⋅s
k = 6977138064900000000♠1.380649×10 kg⋅m⋅k⋅s
na = 7023602214076000000♠6.02214076×10 mol
kcd = 7002683000000000000♠683 cd⋅sr⋅s⋅kg⋅m

in addition ccu proposed that

the international prototype kilogram retired , current definition of kilogram abrogated,
the current definition of ampere abrogated,
the current definition of kelvin abrogated and
the current definition of mole revised.

these changes have effect of redefining si base units, though definitions of derived si units in terms of base units remain same.

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