Smoke from the various Southern California wildfires made Monday's (October 13, 2008) sunset more intense than usual. If wildfire smoke has you seeing red, the reddish tinge to the sun is caused by ‘Rayleigh scattering’ in the atmosphere. Rayleigh scattering – named after English scientist Lord Rayleigh – is the primary mechanism behind both blue sky and orange sunsets, as small particles in the atmosphere (including air molecules) scatter light.