## 前言

1960年，米的定义被改写为由特定光源所发出的光波长（后又改为根据真空光速定义），因此米定义的基准也成为了对自然测量的结果。现今，只留下了千克还是以人造的物品做为定义的基准。
2018年11月16日，第26届国际计量大会一致通过了新国际单位制基本单位定义的提案。新的定义将于2019年5月20日生效。

• 普朗克常数$h=6.62607015\times10^{−34}(J\cdot s)$
• 基本电荷$e=1.602176634\times10^{−19}(C)$
• 玻尔兹曼常数$k=1.380649\times10^{−23}(J\cdot K^{−1})$
• 阿伏伽德罗常量$N_A=6.02214076\times10^{23}(mol^{−1})$

• 光速$c=299,792,458(m\cdot s^{-1})$
• 铯133原子基态超精细能级分裂频率$\Delta\nu(^{133}Cs)_{hfs}=9,192,631,770(Hz)$
• 频率为$540\times10^{12}Hz$辐射的发光效率$K_{cd}=683(lm\cdot W^{-1})$

• $\Delta\nu(^{133}Cs)_{hfs}=9,192,631,770(s^{−1})$
• $c=299,792,458(m\cdot s^{−1})$
• $h=6.62607015\times10^{−34}(kg\cdot m^2\cdot s^{−1})$
• $e=1.602176634\times10^{−19}(A\cdot s)$
• $k=1.380649\times10^{−23}(kg\cdot m^2\cdot K^{−1}\cdot s^{−2})$
• $N_A=6.02214076\times1023(mol^{−1})$
• $K_{cd}=683(cd\cdot sr\cdot s^3\cdot kg^{−1}\cdot m^{−2})$

• 目前千克的定义应废除并使国际千克原器退休
• 目前安培的定义应废除
• 目前开尔文的定义应废除
• 目前摩尔的定义应修改

## 不确定度

Constant Symbol Relation to directly measured and fixed constants (Previous) Significant factor(s) in uncertainty (Previous) Relative uncertainty (Previous) Relation to directly measured and fixed constants (2019) Significant factor(s) in uncertainty (2019) Relative uncertainty (2019)
Mass of IPK $m(\mathcal{K})$ 1 kg None Exact $m(\mathcal{K})$ $m(\mathcal{K})$ $1.2 \times 10^{-8} = u_\text{r}(m(\mathcal{K}))$
Planck constant $h$ $\frac{8 \alpha}{c \mu_0 K_\text{J}^2}$ $K_\text{J}^2$ $1.2 \times 10^{-8} \approx 2 u_\text{r}(K_\text{J})$ $6.62607015\times10^{-34} kg\cdot m^2\cdot s^{−1}$ None Exact
Josephson constant $K_\text{J}$ $K_\text{J}$ $K_\text{J}$ $6.1 \times 10^{-9} = u_\text{r}(K_\text{J})$ $\frac{2 e}{h}$ None Exact
Von Klitzing constant $R_\text{K}$ $\frac{c \mu_0}{2 \alpha}$ $\alpha$ $2.3 \times 10^{-10} = u_\text{r}(\alpha)$ $\frac{h}{e^2}$ None Exact
Elementary charge $e$ $\frac{4 \alpha}{c \mu_0 K_\text{J}}$ $K_\text{J}$ $6.1 \times 10^{-9} \approx u_\text{r}(K_\text{J})$ $1.602176634\times10^{-19} A\cdot s$ None Exact
Magnetic constant $\mu_0$ $4\pi\times10^{-7} m\cdot kg\cdot s^{−2}\cdot A^{−2}$ None Exact $\frac{2 h \alpha}{c e^2}$ $\alpha$ $2.3 \times 10^{-10} = u_\text{r}(\alpha)$
Vacuum permittivity $\varepsilon_0$ $\frac{1}{c^2 \mu_0}$ None Exact $\frac{e^2}{2 h c \alpha}$ $\alpha$ $2.3 \times 10^{-10} = u_\text{r}(\alpha)$
Impedance of free space $Z_0$ $c \mu_0$ None Exact $\frac{2 h \alpha}{e^2}$ $\alpha$ $2.3 \times 10^{-10} = u_\text{r}(\alpha)$
Electron mass $m_\text{e}$ $\frac{16 R_{\infty}}{c^2 \alpha \mu_0 K_\text{J}^2}$ $K_\text{J}^2$ $1.2 \times 10^{-8} \approx 2 u_\text{r}(K_\text{J})$ $\frac{2 h R_{\infty}}{c \alpha^2}$ $\alpha^2$ $4.7 \times 10^{-10} \approx 2 u_\text{r}(\alpha)$
Electron molar mass $M(\text{e})$ $A_\text{r}(\text{e}) M_\text{u}$ $A_\text{r}(\text{e})$ $2.9 \times 10^{-11} = u_\text{r}(A_\text{r}(\text{e}))$ $\frac{2 h R_{\infty} N_\text{A}}{c \alpha^2}$ $\alpha^2$ $4.7 \times 10^{-10} \approx 2 u_\text{r}(\alpha)$
Unified atomic mass unit or dalton \begin{align*}m_u & = 1u \\ & = 1Da\end{align*} $\frac{16 R_{\infty}}{c^2 \alpha \mu_0 K_\text{J}^2 A_\text{r}(\text{e})}$ $K_\text{J}^2$ $1.2 \times 10^{-8} \approx 2 u_\text{r}(K_\text{J})$ $\frac{2 h R_{\infty}}{c \alpha^2 A_\text{r}(\text{e})}$ $\alpha^2$ $4.7 \times 10^{-10} \approx 2 u_\text{r}(\alpha)$
Molar mass constant $M_\text{u}$ $0.001kg\cdot mol^{−1}$ None Exact $\frac{2 h R_{\infty} N_\text{A}}{c \alpha^2 A_\text{r}(\text{e})}$ $\alpha^2$ $4.7 \times 10^{-10} \approx 2 u_\text{r}(\alpha)$
Avogadro constant $N_\text{A}$ $\frac{c^2 \alpha \mu_0 K_\text{J}^2 A_\text{r}(\text{e}) M_\text{u}}{16 R_{\infty}}$ $K_\text{J}^2$ $1.2 \times 10^{-8} \approx 2 u_\text{r}(K_\text{J})$ $6.02214076\times10^{23} mol^{−1}$ None Exact
Atomic mass of carbon-12 $m(^{12}\text{C})$ $\frac{192 R_{\infty}}{c^2 \alpha \mu_0 K_\text{J}^2 A_\text{r}(\text{e})}$ $K_\text{J}^2$ $1.2 \times 10^{-8} \approx 2 u_\text{r}(K_\text{J})$ $\frac{24 h R_{\infty}}{c \alpha^2 A_\text{r}(\text{e})}$ $\alpha^2$ $4.7 \times 10^{-10} \approx 2 u_\text{r}(\alpha)$
Molar mass of carbon-12 $M(^{12}\text{C})$ $0.012kg\cdot mol^{−1}$ None Exact $\frac{24 h R_{\infty} N_\text{A}}{c \alpha^2 A_\text{r}(\text{e})}$ $\alpha^2$ $4.7 \times 10^{-10} \approx 2 u_\text{r}(\alpha)$
Faraday constant $F$ $\frac{c \alpha^2 K_\text{J} A_\text{r}(\text{e}) M_\text{u}}{4 R_{\infty}}$ $K_\text{J}, \alpha^2$ $6.2 \times 10^{-9} \approx u_\text{r}(K_\text{J})$ $e N_\text{A}$ None Exact
Temperature of triple point of water $T_\text{TPW}$ 273.16 K None Exact $T_\text{TPW}$ $T_\text{TPW}$ $5.7 \times 10^{-7} = u_\text{r}(T_\text{TPW})$
Molar gas constant $R$ $R$ $R$ $5.7 \times 10^{-7} = u_\text{r}(R)$ $k N_\text{A}$ None Exact
Boltzmann constant $k$ $\frac{16 R R_{\infty}}{c^2 \alpha \mu_0 K_\text{J}^2 A_\text{r}(\text{e}) M_\text{u}}$ $R$ $5.7 \times 10^{-7} \approx u_\text{r}(R)$ $1.380649\times10^{-23} kg\cdot m^2\cdot K^{−1} \cdot s^{−2}$ None Exact
Stefan–Boltzmann constant $\sigma$ $\frac{256 \pi^5 R^4 R_{\infty}^4}{15 c^7 \alpha^7 \mu_0 K_\text{J}^2 A_\text{r}(\text{e})^4 M_\text{u}^4}$ $R^4$ $2.3 \times 10^{-6} \approx 4 u_\text{r}(R)$ $\frac{2 \pi^5 k^4}{15 h^3 c^2}$ None Exact

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