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Know why the sky is blue? The Color Science of Sky

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Sky, one of the essential elements that we can’t avoid. So, what is the sky? Why the sky is blue? We can answer the question from a different perspective. From a general point of view, what we can see above in the sky. But if we add science to it, the definition would be like this, “Everything in the outer space is simply the sky.”

Earth’s surface which is a section of the sky provides us some elements without which the whole earth can’t be survived. Men have spent their whole life searching for the answer to the question ” Where is the end of the sky?

But still, now it is a mystery. So they declared it as an endless space with infinitely large portions. But now today’s topic is why we can see the sky only blue? Is it possible to see the sky in other colors?

why the sky is blue

So, there is a common myth for the sky appearing blue that is the sunlight is reflected in the ocean. That is totally busted because scientists have discovered the real science behind it.

Why the sky is blue:

Let’s talk about some science. There are mainly two factors. The first one is the atmosphere of the earth and the other one is sunlight. So the earth’s atmosphere consists of three-segments

  1. Gases
  2. water vapor and
  3. droplet Dust

In the gases segment, we find almost 78% of N2 and 21% of O2 and the rest are CO2, Ar, etc. Water vapor and droplets are basically the clouds, and dust is mainly the components that polluted the air.

The other main factor is sunlight. Sunlight is actually white light and a mixture of 7 primary colors which all have different corresponding frequencies and energy. The violet color has the shortest wavelength next is the blue color and then the red one has the highest.

When the sunlight comes across the sky on the earth’s atmosphere, it strikes the air molecule and gets scattered which means air molecule absorbs sunlight and remit it in various direction. But here is the thing, not all the primary colors of the light scattered equally.

The amount of light scattered will be determined by Rayleigh’s law of scattering. Which specifically told that the amount of scattered light or intensity of light is inversely proportional to the fourth power of wavelength of light.

I ∝ 1/ λ4

Where,   I = intensity of light

λ = the wavelengths of light

So if the wavelength is less the amount of scattered light will be more and reversely if the wavelength is more then the amount of scattered light is less.

So, when the sunlight crosses the air surface the lowest wavelength color will be mostly scattered and travel to our eyes. And the lowest wavelength of the 7 primary colors is violet. So technically we should see the sky as violet but it doesn’t happen but why?

There are two reasonable answers. If we see the color spectrum, the amount of blue is huge compared to violet light. And the other reason is humans are more sensitive to blue rather than violet light.

That is the main scientific reason for the sky appearing as blue.

why does the sky sometimes appear white:

sometimes we see the sky full of white. Why??

So the other earth’s atmosphere segments: water vapor, water droplets, and dust is responsible for the sky being white. They also scattered but as they are much bigger with respect to air components of the gases. So unlike the gases, they scattered all the light equally. Then the light is appeared white. In the spring season when there are more water vapors and clouds in the sky then we see the sky as a white one.


Why does the sky look yellow?

As the sunset in our sky, the light has a longer distance to travel through the atmosphere. For this, the blue lights scattered so much that the light does not end up reaching us. Instead of blue, the yellow lights have more possibility to end up reaching towards our eyes. So we the sky turning yellowish.

Why the sky is red at sunset:

There is another question that remains. Why the sky is full of red?

The distance of the sun from us is gradually increasing so lights of more wavelengths have more priority to be seen by our eyes since lower wavelength lights scattered away in the atmosphere. After getting yellowish sky, the red light comes to the atmosphere. It is because the yellow lights keep getting more scattered. Then the yellow and red lights overlap and create an orange color around the sky. Finally, when the sun is about to set, the red light overcomes the yellow light and the sky seems totally red.

Conclusion :

Many authors represent the sky as human life. Humans have so many feelings of happiness, sorrowfulness, anger, depression, and other feelings likely the sky sometimes becomes shining blue, sometimes becomes cloudy white, and sometimes it turns into bloody red. Keeping all the philosophical words aside, we can surely say there is plenty of mystery to solve about the vastness of the sky


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Rayhan Sarwar

I am a glass and ceramic engineering student at the Rajshahi University of Engineering & Technology (RUET). I enjoy exploring science and technology, which is why I chose to study engineering!

This Post Has 2 Comments

  1. Robertalush

    This remarkable phrase is necessary just by the way

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