Fundamental physical constants characterizing black body radiation. The first radiation constant is $$c_{1} = 2\ \pi \ h\ c_{0}^{2}=3.741\,7749(22)\times 10^{-16}\ \text{W m}^{2}$$, the second is $$c_{2} = \frac{h\ c_{0}}{k}=1.438\,769(12)\times 10^{-2}\ \text{m K}$$, where $$h$$ is the @P04685@ $$c_{0}$$ the speed of light and $$k$$ the @B00695@.