The sky looks blue but really it is made up of all the colours as you see on the rainbow. Each of these colours has a different wavelength. Some of these are smoother while others are choppy. Blue light waves travel in short, choppy waves. Like each of the other colours, blue light waves are scattered and reflected as they enter Earth’s atmosphere and collide with gases and other particles. Because the colour blue has the shortest wavelength, it collides with nearly everything in its path and is scattered about the sky. This is why the sky appears blue.