Why is the sky blue? NASA Scientific American

By | September 26, 2018

To understand why the sky is blue, we should consider the nature of the sunlight and how it interacts with the gas molecules that make up our atmosphere. The sunlight, which is white for human eyes, is a mixture of all the colors of the rainbow. Why is the sky blue? NASA

For many purposes, sunlight can be considered as an electromagnetic wave, which causes the particles (electrons and protons) to move up and down in the air molecules through the sunlight through the atmosphere. is.

why is the sky blue nasa

When this happens, the incoming charge generates electromagnetic radiation at the same frequency as the incoming sunlight, but all spreads in different directions. This redirection of sunlight coming by air molecules is called scattering.Why is the sky blue? NASA

The blue component of spectrum of visible light consists of high frequencies compared to red wavelength and red frequency. Thus, as the sunlight of all colors passes through the air, due to the red part of the blue part, the cause of charging particles faster is made. Rapid stimulation, more scattered light is produced, so blue is scattered more strongly than red.Why is the sky blue? NASA

From the wavelength of the visible molecules, the difference is very dramatic for particles like small air molecules. Acceleration of charged particles is similar to the square of frequency, and the intensity of the scattered light is similar to the square of this acceleration.

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The scattered light intensity is therefore proportional to the fourth power of the frequency. The result is that the blue light is scattered almost ten times as red light in other directions efficiently.Why is the sky blue? NASA

When we see an arbitrary point in the sky, away from the sun, we only see the light that was redirected by the atmosphere to our line of sight. Because it is often for blue light compared to red, the sky looks blue.

Purple light is actually slightly more scattered than blue. Most of the Sun’s light entering the atmosphere is blue compared to purple, though, and our eyes are more sensitive to blue light compared to purple light, so the sky looks blue.Why is the sky blue? NASA

The opposite happens when we see the sun setting on the horizon. We only see the light which is not scattered in other directions. The red wavelength of the sunlight that passes through the scattered environment, reaches our eyes, while there is not a brightly scarred blue light.Why is the sky blue? NASA

When the sun is on the horizon, the sunlight travels through the atmosphere, increases the effect – blue light is scattered compared to the upper part of the sun. Thus, the setting sun appears red.

In the polluted sky, small aerosol particles of sulphate, organic carbon, or mineral dust further increase the scattering of the blue light, which sometimes leads to sunsets in polluted conditions.

On the other hand, clouds are made of water droplets which are significantly larger than the wavelength of visible light. The way they disperse the sunlight, it is determined how refracting light is reflected and internally, and spreads around clouds drops.

The difference between the scattering of blue and red lights for these particles is not nearly as large as it is for gas molecules.

Therefore, our eyes receive enough scattered light on all visible wavelengths, making clouds appear more white than blue, especially when blue sky is seen against the background.

Since the sky becomes blue due to scattering from the atmosphere, so the planet in any environment can not have a bright sky.

For example, Apollo on the Moon shows the pictures taken by astronauts, and the surface of the moon is bathed in the sunlight, but there is a completely dark sky in all directions away from the sun.

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