Longer Distance to Travel

During sunsets and sunrises, when the Sun is closer to the horizon, sunlight has to travel through a longer distance and more of the dense environment to reach an observer’s eye.

Sunrise and sunset times in your city

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.

The blue hour

The golden hour

This is why a rising and setting Sun tends to take on spectacular hues of red, orange, and yellow.

Dust and Pollution

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. This is why sunrises and sunsets in rural areas, over the ocean, and deserts are much more vibrant and colorful than over cities and urban areas.

Tips: Take pictures of sunrises and sunsets

Red Moon

Rayleigh scattering is also responsible for giving the Moon a reddish or orange hue during total lunar eclipses. The condition of the Earth's atmosphere, including the amount of pollution and dust from storms and volcanic eruptions, can affect the shade of red the Moon takes on during the eclipse.

When's the next lunar eclipse?

Topics: Astronomy, Sun, Atmospheric Phenomena