Why is the Sky Blue? Check out the answer here

Why is the sky blue? For Sinaumed’s who are still wondering about this, in this article we will discuss it in full. Precisely during the day, especially when the weather is sunny, the color of the sky will look blue. Actually, this one phenomenon is the same as the blue ocean phenomenon. When viewed from a distance, it will appear blue, but when approached, the water will appear clear.

Certainly, curiosity arises in our minds, how can the sky appear blue? Actually this can be explained scientifically. If we used to learn about the refraction of light, we can know the blue color of the sky through one of the sciences of physics.

Causes of Blue Sky

The following are some reasons why the sky is blue.

1. There are short light waves

The source of light in the universe is the Sun. Its white light radiates to the planets that surround the Sun, including the Earth where humans live. When sunlight shines on Earth, the white light passes through Earth’s atmosphere.

In a physics lab, the atmosphere can be likened to a glass prism. Where the Earth’s atmosphere which contains various kinds of gases such as carbon, nitrogen, oxygen, and others will cause light to become fragmented when passing through it.

The split light will turn into different waves. There are long waves and there are some short waves. The long light waves will change to yellow, orange, and also red. Meanwhile, short light waves will be blue and green. These colors can be received by the retina of our eyes.

2. Short Light Waves Scatter in Space

If long light waves could be carried straight up a very long distance, then most of the short waves would be scattered in space. That’s what can make most of the sky blue compared to other colors. The short-wave light actually seems to envelop the Earth, so that the vast sky will also appear blue.

Why is the Sky Blue? The following are the three main factors according to Rayleigh’s theory

It turns out that there are three factors that can affect the color of the sky, namely sunlight, Earth’s atmosphere, and also human vision. However, keep in mind that the blue color of the sky is not caused by the reflection of the blue color in the ocean, as many people have believed so far. The following are three factors that can affect the blue color of the sky.

1. Sunlight

When viewed with the naked eye, sunlight will give the impression of a yellowish white color. However, actually sunlight consists of various colors like the colors of a rainbow, if we look at it from a prism. From there we can see that sunlight consists of various kinds of color spectrum. Where the colors are different waves.

Reporting from the Zenius page, red has a longer wavelength when compared to other colors such as violet and blue. Now, we already know that sunlight has a spectrum of colors and also various waves. So, the question is, why is the sky blue? To answer this question, we need to first identify the components that exist and what actually happens in the Earth’s atmosphere.

2. Earth’s atmosphere

The atmosphere is one of the factors that affect the sky that appears blue. However, what are the particles in outer space? Of course there are many types of particles, with the most abundant notes of Oxygen or O2 and also Nitrogen or N2. The content of nitrogen in the air can reach 78 percent, while oxygen reaches 21 percent. The rest is carbon dioxide, sulfur dioxide, carbon monoxide, and others.

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When sunlight enters the Earth’s atmosphere, there is an interaction between the light and also the particles in the atmosphere. This interaction will cause Rayleigh scattering of light or what can be called Rayleigh Scattering.

Blue and violet light which has a shorter wavelength will be more easily absorbed by molecules in the air. So, the blue and violet light will be more scattered and also scattered.

Then, why is the sky blue, not purple or violet? Given that the wavelength is shorter than blue, this is because the intensity of violet or purple light is lower than that of blue. Below is an illustration of the intensity of the color spectrum emitted by sunlight.

3. Human Sight

Basically, the human eye is more sensitive to blue than to violet. Sunlight, which has various wavelengths and a spectrum of colors, is scattered due to the interaction between light and particles in the atmosphere.

Blue and violet colors with shorter wavelengths are scattered and more abundant than the other colors. Then, our eyes which tend to be more sensitive to blue identify the color of the sky as blue.

Rayleigh Scattering Theory

Why do short light waves make the sky blue? Actually, this can be explained based on Rayleigh scattering theory. According to this theory, the scattering intensity is inversely proportional to the wavelength to the fourth power of the scattering. The scatterer referred to here is the sun. That means, the smaller the length of the wave, the greater the intensity of the scattering.

Blue and violet have shorter wavelengths than the other colors. The maximum solar spectrum is in the blue wavelengths. This is what causes the most dominant visible range scattered by the atmosphere is blue.

The theory of Rayleigh scattering refers to the elastic scattering of light or other electromagnetic radiation by particles that are much smaller than the wavelength of the radiation. According to Rayleigh’s law of scattering, the intensity of the scattered light is inversely proportional to the fourth power of the wavelength of the scattered light. Rayleigh’s law of scattering can be written like this:


So, what do these symbols mean? Simply put, the λ sign refers to the wavelength of light. Therefore, the longer the wavelength, the less scattering will occur. Vice versa, the shorter the wavelength, the more scattering will occur.

Why Can the Sky Also Appear Orange?

If during a clear day the color of the sky becomes blue, then in the morning and also in the evening, we will usually find the color of the sky to be orange. How come? This happens because short light waves will be replaced by long waves.

This change is caused by the sun in the morning and evening looking inclined or not right in the middle. It causes long waves of light to be received. As a result, the sky in the morning and evening will appear orange, yellow or reddish.

Why Does Sunlight Look Yellowish White?

Besides being able to see the blue sky during the day, the sunlight that is visible to the eye will also emit a yellowish white light. How did it happen? Because the spectrum of the Sun that is visible to the eye has passed through scattering particles with lots of scattering in blue and violet colors.

As a result, sunlight will appear yellowish white. At a closer distance, the color of the Sun will appear whiter. This is because light from the sun cannot pass through the scattering particles, so they still contain all the mixed colors.

This is also related to the color of the clouds that look white. The clouds that appear white are caused by water vapor particles whose diameter is above one-tenth the length of the Sun’s wavelength. Therefore, the scattering is not dominantly dependent on the wavelength. The color of clouds that appear white in physics has been explained through the Mie scattering theory. Where cloud particles exposed to sunlight will scatter them into white.

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Blue Sky Associated with Colloids

The color of the sky that looks blue is associated with colloids. Where the air in space is a colloid system. The colloid will be affected by the tyndall effect when exposed to sunlight. After that, the sun’s light will be scattered and then split into various kinds of color waves. The colloid can be called a mixture consisting of two or more substances that are homogeneous. However, the size of the dispersed particles is quite large. So that colloids will be more easily affected by the tyndall effect when exposed to sunlight.

Apart from space, colloids can also be seen anywhere. For example, in milk, clouds, and also clouds. The cytoplasm inside the cell is also an example of a colloid.

Tyndall effect

As previously explained that colloids will be affected by the Tyndall effect when exposed to sunlight. So what is the Tyndall effect? The Tyndall effect is an effect that occurs when a solution is exposed to light. When a true solution is exposed to light, the light will not be scattered. Because colloidal particles have a relatively larger size to scatter light. Likewise, in a true solution, the particles are relatively small, so the scattering of light will be very small and difficult to observe.

The Sky on Earth is Inversely Compared to the Sky in Space

Unlike the sky on Earth, where we usually see it in blue, the sky in outer space will look darker. In fact, the distance to the Sun is relatively closer. So, actually outer space itself is pitch black, but that doesn’t mean it’s dark without light.

We can take the example of a room with windows painted black. Is it during the day in the room can not be seen anything? Absolutely not. We can apply this example to answer questions related to why the sky in outer space looks darker.

Outer space is a vacuum, so nothing can reflect light. In addition, outer space consists of 4.9 percent matter, such as planets, gas, stars, and so on, then about 26.8 percent contains Dark Matter. Meanwhile, about 68.3 percent contains something called Dark Energy. This causes outer space to appear darker and blacker.

We can point the flashlight over an empty space. Then the light coming from the flashlight will not have any effect. Such is the analogy of dark outer space. So, no matter how many stars there are in space, if there is nothing to reflect light, it will cause conditions to remain dark.

The Role Of The Atmosphere Is Very Important

As explained above, that sunlight that has penetrated the atmosphere is one of the reasons why the sky is blue or causes other colors on Earth. This atmosphere also serves to reduce radiation from sunlight during the day. Meanwhile at night, the function of the atmosphere is to remove excess heat.

If there was no atmosphere, then surely the sun’s rays would not be able to reach the Earth and the sky, as it is now, would not occur either. Not only that, if 100 percent of the sun’s radiation reaches Earth without passing through the atmosphere, then we can be sure that our planet is no longer a good place to live. Because there will be no human being who can survive when exposed to radiation from the Sun in full. So it should be as living things that live on Earth to always protect nature and also the environment so that it remains sustainable.

Thus the explanation of why the sky is blue and the theory that discusses it. Hopefully every discussion in this article can provide benefits as well as add to your insight.