Why is evening sun red

Sometimes you can see a gradation of color across the surface of the sun. If you saw a sunset on the moon, our local star, the sun, would look white. But, unlike the moon, Earth does have an atmosphere. And most of us know that white light — like sunlight — is composed of all the colors of the rainbow. Tiny molecules in our atmosphere cause light to scatter.

Think about what happens as the sun sinks lower in the sky. When the Sun is high in the sky, the light has to travel a shorter distance through the atmosphere. This means most of the yellow, orange, and red light passes through while a small amount of blue and purple light is scattered and removed from the mix. The Sun, therefore, looks yellow for us here on Earth. Due to Rayleigh scattering, most of the light of shorter wavelengths — the blue, violet, and green — are scattered away multiple times, leaving only lights of longer wavelength — the red, orange, and yellow — to pass straight through to the observer.

This is why a rising and setting Sun tends to take on spectacular hues of red, orange, and yellow. The quality of the air that sunlight has to pass through also has an effect on the color of sunrises and sunsets. Dust particles and pollutants tend to tone down the colors in the sky as well as impede light from reaching the observer on the ground.

Because of this, the sky takes on dull hues of red and yellow when the air is full of dust and pollutants. The weather could be well-determined by the amount of water vapor and dust particles in the atmosphere.

A red sky indicates a high volume of moisture particles and dust, in which red wavelengths break through the atmosphere. Blue particles can pass through easier and more light is spread making it easier to see and the most visible color in the sky. A red hue in the night sky comes from a setting sun that sends its light through a high concentration of dust particles.