Why are sunsets red?

Sunsets often have a red or orange color to them. Why is this? Sunlight (what we call "white light") is made up of all different colors of light, each having a different wavelength. During a sunset, more red light is scattered toward you because of aerosols in the lower atmosphere, compared to the amount of blue or green light. Since, at sunset, sunlight is passing through a much longer path of the lower atmosphere than when the sun is overhead, the effect of the aerosols becomes much stronger. So, you end up seeing more red light that any of the other colors of light, and the sky appears red.