Dear Tom,
Why does the color of the sun change from red at sunrise to white at noon?
—Margaret Wellings
Dear Margaret,
It is due to the affects of the atmosphere. Pure sunlight is white. If viewed from a vantage point above the Earth’s atmosphere, the sun would always appear white. Every color of light has its own special wavelength, but when blended all together, white results.
When sunlight shines through air, its component colors are scattered into their separate wavelengths. When sunlight in shining straight down, or nearly so —at noon—sunlight is scattered less and appears white. When near the horizon, sunlight travels a greater distance through the atmosphere and more scattering occurs. Only the longer wavelengths, the reds, make it through to our eyes and so the sun appears red.