How do you appreciate the role of molecules in the atmosphere for the blue colour of the sky ?

Explanation

1) The sky appear blue due to atmosphere refraction and scattering of light through molecules.
2) Molecules are scattering centres.
3) The reason to blue sky is due to the molecules `N_(2)` and `O_(2)`.
4) The sizes of these molecules are comparable to the wavelength of blue light.
5) In the absence of molecules there will be no scattering of sunlight and the sky will appear dark.
6) We should appreciate the molecules which are scattering centres.