Why does the sky turn red at sunset?
When the sun is low in the horizon, the sunlight has to travel through more particles in the atmosphere. You see sunlight as white, but it’s made up as a combination of the colors of the spectrum. Those particles will tend to scatter away the blue and green light part of the sunlight’s spectrum, leaving behind the more-difficult-to-scatter red and orange colors. That’s because red and orange lights has a longer wavelength than the blue and greens, making it less affected by particles. Pollution, ash or smoke can enhance the colors as there’s more particles to scatter away the shorter-wavelength part of the spectrum.