by Chris Peterson » Sat Apr 23, 2022 9:04 pm
johnnydeep wrote: ↑Sat Apr 23, 2022 7:13 pm
Chris Peterson wrote: ↑Fri Apr 22, 2022 9:40 pm
johnnydeep wrote: ↑Fri Apr 22, 2022 9:24 pm
Again, though, why are we able to see the scattered light at all? Why doesn't "scattering" imply it's being bounced around more and so we should see less of it?
What would you expect the sky to look like if no light were scattered? Scattered light is ALL we can see! The only direct light is looking straight at the Sun. We see scattered light because as the shorter wavelengths bounce around off of air molecules, some of those photons get diverted in our direction and make it to our eyes.
Still having trouble with this, but...
Hmm, so the light from the Sun that makes it to us "more directly"(*) is responsible for the color of the Sun we perceive, but the scattered light is responsible for the color of stuff (atmosphere) that's causing the scattering?
(*) - I say "more directly" because I would think that most visible photons from the Sun must get scattered somewhat on their way through the atmosphere simply from probabilistic standpoint.
Yes, the scattering affects all wavelengths, it's just that the shorter visible wavelengths are more likely to scatter. If you look at the sky spectroscopically, it's a continuum, just weighted towards the shorter wavelengths. Which we see as blue. (Larger particles scatter by a different mechanism, Mie scattering, which isn't very wavelength dependent, which is why we see clouds and fog and overcast as white.)
If you consider the path of a photon, those that come on a direct path from the Sun will have more short wavelength ones knocked out of the path, so we see the Sun appear a bit yellowish. Those that come by any other path will have been scattered one or more times, with each scattering event selectively favoring shorter wavelengths. So we'll see more short wavelength photons than long.
[quote=johnnydeep post_id=322290 time=1650741181 user_id=132061]
[quote="Chris Peterson" post_id=322271 time=1650663648 user_id=117706]
[quote=johnnydeep post_id=322270 time=1650662662 user_id=132061]
Again, though, why are we able to see the scattered light at all? Why doesn't "scattering" imply it's being bounced around more and so we should see less of it?
[/quote]
What would you expect the sky to look like if no light were scattered? Scattered light is ALL we can see! The only direct light is looking straight at the Sun. We see scattered light because as the shorter wavelengths bounce around off of air molecules, some of those photons get diverted in our direction and make it to our eyes.
[/quote]
Still having trouble with this, but...
Hmm, so the light from the Sun that makes it to us "more directly"(*) is responsible for the color of the Sun we perceive, but the scattered light is responsible for the color of stuff (atmosphere) that's causing the scattering?
(*) - I say "more directly" because I would think that most visible photons from the Sun must get scattered somewhat on their way through the atmosphere simply from probabilistic standpoint.
[/quote]
Yes, the scattering affects all wavelengths, it's just that the shorter visible wavelengths are more likely to scatter. If you look at the sky spectroscopically, it's a continuum, just weighted towards the shorter wavelengths. Which we see as blue. (Larger particles scatter by a different mechanism, Mie scattering, which isn't very wavelength dependent, which is why we see clouds and fog and overcast as white.)
If you consider the path of a photon, those that come on a direct path from the Sun will have more short wavelength ones knocked out of the path, so we see the Sun appear a bit yellowish. Those that come by any other path will have been scattered one or more times, with each scattering event selectively favoring shorter wavelengths. So we'll see more short wavelength photons than long.