The Science Behind Why the Sky is Blue - Debunking Common Misconceptions

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In summary, the reason why the sky appears more blue towards the zenith on a clear day is due to the rotation of the Earth and the Doppler Effect. As the Earth rotates, the distance between a particular region and the Sun changes, causing the wavelength of sunlight to change and appear more blue during most of the day. This phenomenon is known as Rayleigh's Blue Sky Law. The upper atmosphere is actually less dense, not denser, and temperature does not affect the color of the atmosphere. The difference in brightness between the horizon and zenith is due to the amount of light-scattering particles in the line of sight, with more particles present near the horizon.
  • #1
Dx
On a clear day, the sky appears to be more blue toward zenith than it does towards the horizon. why?
I thought it was because the atmosphere is denser higher up than it is at the Earth's surface but a friend told me "the temp of the upper atmosphere is higher than its at the Earth's urface and that's why?" is he correct? we did some research on google and it kind of talked about both but he still argues he's right and I am wrong. So which is it?
dx :wink:
 
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  • #2
I think your explanation is more correct than your friend's, but I do not think it is the correct one.

I think it has something to do with the rotation of the Earth and the Doppler Effect. During a day, a particular region of the surface of the Earth will get closer and closer to the sun in the morning, and further away from the sun as it approahces afternoon due to its rotation aroundthe Earth. As the distance between the particular region of the surface of the Earth and the Sun changes, the wavelength ofthe sunlight that shines on the surface of the Earth changes. As the sun approaches the particular region of the Earth, the wavelength of the sulight is "compressed", and that means the frequency of the sunlight is increased and therefore the sky will appear to be blue during most of the day. And as the particular region of the surface of the Earth turns away from the Sun, the wavelength of the sunlight is "stretched", therefore the colour of the sky durgin sunrise and dawn appears to be red.

You shold really look up Rayleigh's Blue Sky Law. But I'm pretty confident my explanation is correct.
 
  • #3
That response was a joke, right? The "blue sky" remark was to let us know that, right?

Just on the chance that someone didn't realize that: light waves are not "compressed" or "stretched" passing through the atmosphere. The distance from the Earth to the sun is over 93 million miles- the atmosphere directly over head is not signifcantly "closer" to the sun than any other part.

By the way, DX, the upper atmosphere is LESS dense, not denser. However, temperature also has nothing to do with the color of the atmosphere.
 
  • #4
More blue? WHOA!
Well, every painter knows (or should know) that a cloudless sky appears brighter towards the horizon, and darker towars the zenith. I think this is because near the horizon, the line of sight crosses more distance inside the atmosphere, i.e. there are more light-scattering particles in the line of sight.
 

1. Why is the sky blue during the day?

The sky appears blue during the day because of a phenomenon called Rayleigh scattering. This occurs when sunlight enters the Earth's atmosphere and interacts with the molecules in the air. The shorter, high-energy blue wavelengths of light are scattered more efficiently than the longer, low-energy red wavelengths. This causes the blue light to scatter in all directions, making the sky appear blue to our eyes.

2. Is the sky blue because of the ocean's reflection?

No, the sky is not blue because of the ocean's reflection. While the ocean can reflect blue light, it is not the primary reason for the blue color of the sky. As mentioned before, the blue color is due to the scattering of sunlight by the Earth's atmosphere.

3. Does pollution make the sky appear more blue?

Contrary to popular belief, pollution actually makes the sky appear less blue. This is because pollutants in the air can scatter and absorb different wavelengths of light, making the sky appear hazy and less vibrant. In areas with high levels of pollution, the sky may even appear gray or brown instead of blue.

4. Why does the sky sometimes appear pink or orange during sunrise and sunset?

During sunrise and sunset, the angle of the sun is lower in the sky, meaning sunlight has to travel through more of the Earth's atmosphere to reach our eyes. This causes more of the blue light to be scattered, leaving behind longer, redder wavelengths of light. This gives the sky a pink, orange, or even red appearance during these times.

5. Is the sky always blue on other planets?

No, the color of the sky on other planets can vary depending on their atmospheric composition. For example, Mars has a thin atmosphere made up mostly of carbon dioxide, causing its sky to appear reddish-orange. Venus has a thick atmosphere made up of sulfuric acid clouds, giving its sky a yellowish appearance. The blue color of Earth's sky is due to our specific atmospheric conditions, including the amount of nitrogen and oxygen present.

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