(1) At first, people (THINK) ________ the sky was blue because there were water droplets in it, but if that were true you (GET) ________ a deeper blue when the air is more humid and that's not the case. (2) After a little more investigation, it (REALISE) ________ that the blue was due to the air molecules in the atmosphere. (3) The light from the sun is made up of many different colours, each of which is a different wavelength of light. (4) The wavelength of red, for example, is longer than the wavelength of blue.

(5) (LONG) ________ wavelengths for the most part travel straight through air molecules, while shorter ones are more scattered by (THEY) ________.

(6) So when the blue wavelengths hit the air molecules, they are scattered all over the sky ‒ and that's what you see when you look up.

(7) At sunset, when the sun is lower on the horizon, its light has (TRAVEL) ________ through many more air molecules than when it is right above us. (8) All these molecules scatter the red wavelengths, too, and that's why the sun (LOOK) ________ red at the end of the day.