Rayleigh scattering

Rayleigh scattering is the process of light (like from the sun) being scattered in all directions by small particles. When light hits these small particles, the light bounces off in different directions, just like when you throw a ball at a wall and it bounces off in many directions. This is why the sky is blue- the small particles in the air scatter the blue part of light more than the other colors, so we see a lot of blue!