2 ms·

I just need an ELI5 of that Wikipedia page and I’m all set. Good find though.

bityard 5y ago
This reminds me of the time I went looking for a satisfactory answer for why the sky is blue. It turns out a surprising number of people have a surprising number of different opinions and explanations on this. You pretty much need a PhD in physics to fully grok most of them. And every time you think you've read something that at least _sounds_ concrete, someone else comes along and says, "yes and no, the _real_ mechanism is this," ad infinitum until you wind up on the fringes of scientific knowledge. In the end, hours of research later, as best as I could tell, it came down to: the sky is blue because air is blue. But it's a very faint blue, so you can't actually discern the blue until you look through a _lot_ of air, for example in the sky.
- mleonhard 5y ago
  > the sky is blue because air is blue. Things have color because they scatter/reflect/refract/absorb/emit differently for different colors of light. Air looks blue because it scatters blue light more than other colors. The blue components of sunlight reach you from all parts of the sky, while the non-blue components reach you mostly from the direction of the sun. At sunset, sunlight from the direction of the sun passes through much more atmosphere than during the day and most of its blue light scatters away, leaving red and yellow. [0] If air didn't scatter light, the sky would be black like it is on the moon. Air is a gas. Gasses do not reflect light. Air refracts sunlight and makes the sun appear flattened at the horizon [1]. Air absorbs most non-visible colors (UV and IR) [2]. Animals evolved eyes to see only the colors of available light. During aurora, the air emits green light. [0] https://en.wikipedia.org/wiki/Rayleigh_scattering https://en.wikipedia.org/wiki/Rayleigh_scattering [1] https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Refractive_index https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Refractive... [2] http://funnel.sfsu.edu/courses/metr104/F13/summaries/AbsorptionSpectra_Atmosphere.pdf http://funnel.sfsu.edu/courses/metr104/F13/summaries/Absorpt...

This reminds me of the time I went looking for a satisfactory answer for why the sky is blue. It turns out a surprising number of people have a surprising number of different opinions and explanations on this. You pretty much need a PhD in physics to fully grok most of them. And every time you think you've read something that at least _sounds_ concrete, someone else comes along and says, "yes and no, the _real_ mechanism is this," ad infinitum until you wind up on the fringes of scientific knowledge. In the end, hours of research later, as best as I could tell, it came down to: the sky is blue because air is blue. But it's a very faint blue, so you can't actually discern the blue until you look through a _lot_ of air, for example in the sky.

mleonhard 5y ago
> the sky is blue because air is blue. Things have color because they scatter/reflect/refract/absorb/emit differently for different colors of light. Air looks blue because it scatters blue light more than other colors. The blue components of sunlight reach you from all parts of the sky, while the non-blue components reach you mostly from the direction of the sun. At sunset, sunlight from the direction of the sun passes through much more atmosphere than during the day and most of its blue light scatters away, leaving red and yellow. [0] If air didn't scatter light, the sky would be black like it is on the moon. Air is a gas. Gasses do not reflect light. Air refracts sunlight and makes the sun appear flattened at the horizon [1]. Air absorbs most non-visible colors (UV and IR) [2]. Animals evolved eyes to see only the colors of available light. During aurora, the air emits green light. [0] https://en.wikipedia.org/wiki/Rayleigh_scattering https://en.wikipedia.org/wiki/Rayleigh_scattering [1] https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Refractive_index https://en.wikipedia.org/wiki/Atmosphere_of_Earth#Refractive... [2] http://funnel.sfsu.edu/courses/metr104/F13/summaries/AbsorptionSpectra_Atmosphere.pdf http://funnel.sfsu.edu/courses/metr104/F13/summaries/Absorpt...