Why the sky is blue ?

A large number of particles fly in the air that surrounds the earth – these are various gases, dust particles, water particles, etc. When a white ray from the sun (and, as you remember, it is not by itself, but all the colors together) hits the air, then colliding with air particles and particles that fly in the air, it begins to crumble into the colors of which it consisted.
It turned out that not all colors are equally bright, some are very clumsy, they scatter in the air, colliding with some particles, while others, very fast, dodge collisions and reach the Earth.
Blue rays are clumsy, they more often than others hit obstacles and scatter (fly away) on all sides, illuminating the air with blue light.