The phenomenon of the blue sky was explained by Lord Rayleigh, a British physicist, in the late 19th century.

He developed the theory of Rayleigh scattering, which describes how light interacts with particles in the atmosphere.

Here's a simplified explanation:

* Sunlight is made up of all colors of the rainbow.

* When sunlight enters the atmosphere, it hits tiny particles (like nitrogen and oxygen molecules).

* These particles scatter the light, meaning they change the direction of the light waves.

* Blue light, with its shorter wavelengths, is scattered more effectively than other colors.

* This scattered blue light is what we see as the blue sky.

So, while others had observed the blue sky and made attempts to explain it, Lord Rayleigh was the first to develop a comprehensive and scientifically accurate explanation.