Blue Sky
A blue sky (青空\あをぞら\アオゾラ, aozora), for the most part, is a sky that looks blue if the weather is clear or sunny during the morning or early evening hours.
It does not matter whether there are clouds or not (probably), but a cloudy sky with so many clouds that the sky appears white is not called a blue sky. In such a case, a blue sky appears as peeking through the clouds.
Even though the sky color appears endless from the ground, it actually lasts only as far as the atmosphere. If you rise to the point where the sky is no longer blue, you are not in the sky, but in what is written as space.
The sky appears blue because of the atmosphere. The color of the sky is the color of light scattered by dust and other particles in the atmosphere, and light with shorter wavelengths is more easily scattered, making the sky appear blue to the human eye.
