# Color of Sky Without Atmosphere or 50 Times Densers

1. Sep 29, 2011

### JSGandora

Color of Sky Without Atmosphere or 50 Times Denser

What would be the color of the sky if the Earth had no atmosphere?

Since the scattering of light is due to the fact that the wavelengths of blue are small enough to be obstructed by the particles in the atmosphere, whereas longer wavelengths would be obstructed less, would the Earth having no atmosphere mean that the color of the sky be entirely black with a bright white spot which is the sun?

Also, what would happen if the Earth's atmosphere was 50 times denser than it is?

Lastly, my physics books says that "scattering decreases, in fact, as $\frac{1}{\lambda ^4}$" and gives no further elaboration. Can anyone tell me what this means?

Last edited: Sep 29, 2011
2. Sep 29, 2011

### xts

Yes, the sky would be black with stars visible even during the day. You may want to watch some photos made from orbital stations and long time ago from Moon. Or even compare the sky viewed from ground level with the look from an airplane, travelling 10,000m higher, where atmosphere is over twice less dense.

The question about 50 times dendier atmosphere is non-physical - so dense atmosphere would have to differ from our in many factors, especially it would be always cloudy (like atmosphere of Venus is), so you'd never see the sky.

Reyleigh's scattering, which is responsible for blue sky and red sunsets is much stronger for short wavelengths of light than for long one - that's why the sky is blue.
See: http://en.wikipedia.org/wiki/Rayleigh_scattering

3. Sep 29, 2011

### JSGandora

I see, thanks. So what you're trying to say is, that if the atmosphere is 50 times denser, then we would never see the sky? Is that only because of the clouds on venus? What if there were no clouds? What would you see then?

Also, thanks for the wikipedia page, however I'm still confused about scattering decreases as $\frac{1}{\lambda^4}$.