Why Is the Sky Blue?

At first, people thought the sky was blue because there (1) _______ water droplets in it but if that were true you'd get a deeper blue when the air is more humid and that's not the case.

After a little more investigation, it (2) _______ that the blue was due to the air molecules in the atmosphere. The light from the sun is made up of many different colours, each of which is a different wavelength of light. The wavelength of red, for example, is (3) _______ than the wavelength of blue.

Longer wavelengths for the most part travel straight through air molecules, while shorter ones are more (4) _______ by them.

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.

At sunset, when the sun is (5) _______ on the horizon, its light has to travel through many more air molecules than when it is right above us. All these molecules scatter the red wavelengths, too, and that's why the sun (6) _______ red at the end of the day.