The air quality today was terrible due to the smoke drifting in from wildfires in Canada. On the positive side, the sunset was spectacular. Wildfires cause highly vibrant, intensely red and orange sunsets primarily due to a physics phenomenon known as Mie scattering. Under normal conditions, clean air particles are tiny and scatter short wavelengths of light—like blue and violet—which is why the midday sky looks blue. However, wildfire smoke pumps millions of much larger particulate matter and aerosols into the upper atmosphere. Because these smoke particles are significantly larger than standard air molecules, they act as an aggressive filter. They completely scatter away the shorter violet, blue, and green wavelengths of light. This allows only the longest wavelengths—vivid oranges and deep reds.