Science is Fun Fridays!

 

San Francisco

Smoke may be hydrocarbon particles or soot, which is black carbon.  Carbon atoms absorb and scatter more longer wavelength red hues than shorter wavelength blues, absorbing more of the blue, so we see this red-orange sky.  

Since it's San Francisco, we know there is also a layer of fog.  Water vapor absorbs more on the red-orange side of the spectrum, but water molecules are larger than carbon, so they scatter all wavelengths.  What is normally grayish in color was filtered by the smoke, multiplying the scatter.

People said it was like being on Mars, but scientists are quick to correct that.  Mars appears red due to the dust in the thin atmosphere, and what we're seeing is more like Saturn's moon, Titan.  A thick atmosphere with blue scattering hydrcarbons.

Physicist Sanaz Vahidinia says of the location of the smoke cloud: "If it's pretty high and pretty thick, then it'll play a role in how subdued the light is.  It won't be vivid."

Wired