Why Do Sunsets Look Red?
In the evening, when the sun is near the horizon, the sun may look red, and the sky may glow with the warm colors of a sunset. Of course, the sun itself hasn’t changed color. It merely looks red to us at that particular time of day.
At sunset, when the sun is low in the sky, we see the sun through a much thicker band of the earth’s atmosphere. When sunlight passes through the atmosphere from this angle, the shorter blue rays we see during the day are filtered out.
This leaves only the longer orange and red rays for us to see. As a result, the sun and the western sky look red. Sunset colors are typically more brilliant than sunrise colors, because the evening air contains more particles than morning air.