Why is The Sky Blue?

When you looked up and see the clear blue sky, have you ever wondered why is it’s blue? Why isn’t it pink or grey or yellow? Well here is my research on why, is the sky blue.

To understand why the sky is blue, we need to consider the nature of sunlights and how it interacts with the gas molecules that make up our atmosphere. The sunlight that appears white to the human eye, actually consists of the seven primary color where each one of them has a corresponding frequencies and wavelength associated with it; the violet color light has the shortest wavelength of all while the red one has the longer wavelength.

The fact that light has a different wavelength means that each will respond differently to interactions. It is known that unless something gets in the way like for example a mirror that reflects it, a prism that bends it, or even a molecules that scatters it; all lights should travels in a straight line. Since the molecules in our atmosphere – like nitrogen, oxygen, water, carbon dioxide, as well as argon atoms – are all much smaller than the wavelength of light itself, the shorter the light’s wavelength is, the better it scatters. So when the sunlight reaches earth’s atmosphere, the molecules in the air will mostly scatter the shorter waves of blue light while most of the red, yellow and green wavelength of light pass straight through the atmosphere to our eyes.

In another word, when the sun is high in the sky, it makes the entire sky blue because you are actually seeing the blue light scattering around the atmosphere.

So why is the sky a different color at sunset?

As the sun goes lower in the sky (the closer to the horizon it is) the more atmosphere the light must pass through to reach you. The bluer light gets scattered away, in all directions, while the redder light is far less likely to get scattered, meaning it arrives at your eyes. In a polluted sky, small aerosol particles of sulfate, organic carbon, or mineral dust further amplify the scattering of blue light, making sunsets in polluted conditions sometime spectacular.