Why is the sky blue? A layman's approach

As we are human beings, we all are curious – an intrinsic behavior that is associated with us. As any curious being would be, we are also very aware of our environment and the changes that happen to it- we are very good at noticing changes that we even have developed many models and theories explaining the planet we live in. It would be very hard to imagine the level we have developed into right now. A few centuries ago, planes were unimaginable and now we have supersonic jets. We have sent probes to Mars and other bodies of the Solar System. Even more, we have developed models that explain exotic celestial bodies found millions of lightyears away.

As a species who have been through a lot and have come this far, it would not be wrong- at all- to assume that we are curious about the environment we live in. It is the curiosity we had that has brought us this far. One very obvious thing we can question since we were, perhaps, children is why the sky is blue as viewed from the Earth. Although the answer is a bit scientific, some people try to attribute the phenomena with the existence of water on the planet- which, perhaps would be more valid, if the question was about the Earth’s appearance from an outsider’s point of view(An outsider is an observer not on the Earth’s surface, for instance, someone who is standing on the Moon – or Sun(if, hypothetically possible))

SO – why is the Sky Blue? It all depends on what kinds of light we get from the sun. By kind’s, we are talking about the components of the light we see. So, generally the light our eyes can see that come from the sun is called the Visible Light Spectrum. The Visible Light Spectrum is part of the Electromagnetic Spectrum that our eyes can see and it consists of lights of color in increasing frequency, red, orange, yellow, green, blue, indigo, and violet – the colors of the rainbow. So, it is important to note that the light that comes to the Earth is not a single white light, but a combination of all the colors.

Picture credit: NASA

If light is composed of many colors, then when refracted, it diffuses into the different component colors. So, the shorter the wavelength(the higher the frequency), the more the light color gets refracted( it is called Rayleigh scattering). So, violet and indigo, then blue and the other colors get refracted. Why don’t we have a violet sky? Our eyes are not suited to observing violet light – we lack violet light receptors in our cons, hence the color of the sky we can see is the next strongest, which is blue.

That’s why the sky is blue.

Aaron G. Kebede
Aaron G. Kebede
Research Assistant