Sunrise and Sunset Colors
When the Sun is low in the sky, during sunrise and sunset, sunlight travels through a much greater thickness of atmosphere than it does when it is overhead. Earth's atmosphere contains molecules of gas, mostly nitrogen and oxygen, as well as smaller amounts of carbon dioxide, aerosols, dust, and ozone. These particles scatter wavelengths of light. When the Sun is low in the sky, and the light travels through a greater distance of atmosphere, light comes in contact with more particles and more wavelengths of light are scattered including longer wavelengths like green, yellow and orange. Only the red light comes through to your eyes. So, the setting sun often looks red!