Would the sky be red if the atmosphere was thicker?

In summary, if Earth's atmosphere had the same composition of gases, the sky would be red instead of blue because the light from the Sun would have to travel through more atmosphere.
  • #1
willstaruss22
108
1
Lets say Earths atmosphere with the same composition of gases was 500 bar. Would the sky be red instead of blue because light from the Sun would have to travel through more atmosphere?
 
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  • #2
The sun itself would be very red. I dont't think the sky would have to be red, as the light that you see would still be the part of the sunlight that is scattered. At sunrise/sunset, the sunlight will take a much longer path through the atmosphere, and only the sun itself and the sky close to it is red.
 
  • #3
willem2 said:
The sun itself would be very red. I dont't think the sky would have to be red, as the light that you see would still be the part of the sunlight that is scattered. At sunrise/sunset, the sunlight will take a much longer path through the atmosphere, and only the sun itself and the sky close to it is red.
If the atmosphere was thicker,wouldn't the sun look red even at noon?
 
  • #4
adjacent said:
If the atmosphere was thicker,wouldn't the sun look red even at noon?

Yes. What I meant was, that sunset/sunrise with a normal Earth atmosphere mimics the situation with a much thicker atmosphere.
 
  • #5
So at noon the sky would essentially still be blue but the Sun would look red?
 
  • #6
willstaruss22 said:
So at noon the sky would essentially still be blue but the Sun would look red?

With a thicker atmosphere, not only blues would be scattered away from the direct path from the Sun. I imagine that you would also see green parts of the spectrum being scattered in the sky, away from the Sun. This could give a more Cyan tint to the sky. This is the sort of colour you can see in the western sky near sunset, where the atmospheric path is long and the normal blue of the sky becomes 'tainted' with a greenish hue and makes that very attractive, temporary greeny blue which we all recognise as a precursor to darkness.
With a really thick atmosphere (we have to mean 'dense' here, too) the outline of the Sun would also become blurred by scattering (as we get when viewing the Sun through thin cloud at sunset).
 
  • #7
It seems to me that the sky would simply be a more intense and brighter blue, since even more blue light would be being scattered. Can someone tell me if this thought is incorrect? I would greatly appreciate it. Thanks.
 
  • #8
500 bar? The blue parts would get absorbed long before they reach the surface, and I guess the red parts would get scattered so much you would not see the sun as a disk any more, just a general very dim red glow of the sky.
Note that nitrogen and oxygen are beyond their critical point then, that might change the absorption.
 
  • #9
Maybe I should change the question a little - what if the normal depth of the atmosphere was the distance light travels through the atmosphere at sunset, when the sun is red? Would the whole sky be red, or just a deeper blue?
Also, another question: when you look out over a flat landscape on fairly clear day, and see a layer of clouds (discrete clouds) at maybe all the same height above the earth, stretching away in the distance and seemingly getting closer to the Earth as they near the horizon, are you, in a sense, seeing the curvature of the earth?
 
  • #10
bunchie said:
what if the normal depth of the atmosphere was the distance light travels through the atmosphere at sunset, when the sun is red?
Of the order of ~200-300km at sea level pressure. You get a similar effect with less than 50 bar surface pressure and the sun directly above you - but then blue light gets a really hard time reaching the surface, so the rest of the sky will probably look dark red.
 

1. Why is the sky blue instead of red?

The color of the sky is due to a phenomenon known as Rayleigh scattering, where the Earth's atmosphere scatters sunlight in all directions. Blue light has a shorter wavelength and is scattered more easily, making it the dominant color we see in the sky.

2. Would a thicker atmosphere change the color of the sky?

Yes, a thicker atmosphere would change the color of the sky. This is because a thicker atmosphere would scatter more light, causing longer-wavelength colors like red to become more dominant.

3. How much thicker would the atmosphere need to be for the sky to appear red?

The exact amount of thickness needed for the sky to appear red would depend on various factors such as the composition of the atmosphere and the amount of light it receives. However, in general, a significantly thicker atmosphere would be needed to noticeably change the color of the sky.

4. Would a thicker atmosphere have any other effects on the sky?

Yes, a thicker atmosphere would have other effects on the sky. For example, it could make the sky appear more hazy or opaque, as more light would be scattered and absorbed by the atmosphere. It could also change the appearance of sunrise and sunset, as the thicker atmosphere would cause more refraction and dispersion of light.

5. Are there any planets with thicker atmospheres where the sky appears red?

Yes, there are planets with thicker atmospheres where the sky appears red, such as Mars. This is because Mars has a much thinner atmosphere compared to Earth, and the dust particles in its atmosphere are larger and able to scatter longer-wavelength colors like red more efficiently.

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