This photograph of a rust-colored sunset was taken from Emerald Isle, part of the famous "Outer Banks" of North Carolina. Emerald Isle's island geography is at least partly responsible for the sunset's brilliant orange hue.

The sun emits "white" light. White light is actually a combination of all the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. Scientists and artists often use the acronym Roy G. Biv to remember these colors of the visible light spectrum. All colors have different wavelengths, from the very long (Roy) to the very short (Biv).

The sun's white light is scattered by billions of tiny molecules as it filters through Earth's atmosphere. Light with short wavelengths (Biv) scatters much more easily than light with long wavelengths. Because of this, the sky usually appears blue as the sun shines down through the atmosphere during the day.

As the sun rises and sets, however, its light passes through much more of Earth's atmosphere before reaching our eyes. Blue and violet light are scattered away. Only the long, reddish wavelengths can go the distance.

What does all of this scattering have to do with brightly colored island sunsets? It comes down to what does the scattering.

Earth's atmosphere—air—is mostly nitrogen and oxygen. Those molecules are pretty evenly spread out and do most of the sunlight-scattering around the world. Islands, however, are very close to the ocean. The air above them is filled with many more water and salt molecules than air further inland. All these "extra" molecules scatter even more blue light, leaving even more red light to reach our eyes.

Noun

layer of gases surrounding Earth.

Noun

layers of gases surrounding a planet or other celestial body.

emit
Verb

to give off or send out.

filter
Verb

to remove particles from a substance by passing the substance through a screen or other material that catches larger particles and lets the rest of the substance pass through.

Noun

study of places and the relationships between people and their environments.

Noun

body of land surrounded by water.

molecule
Noun

smallest physical unit of a substance, consisting of two or more atoms linked together.

nitrogen
Noun

chemical element with the symbol N, whose gas form is 78% of the Earth's atmosphere.

Noun

large body of salt water that covers most of the Earth.

Outer Banks
Noun

barrier islands off the coast of the U.S. state of North Carolina.

oxygen
Noun

chemical element with the symbol O, whose gas form is 21% of the Earth's atmosphere.

Noun

multicolored arc produced by sunlight striking raindrops.

Roy G. Biv
Noun

device used to remember the colors of the visible spectrum: red, orange, yellow, green, blue, indigo, violet.

scatter
Verb

to disperse or distribute without a clear pattern.

sunset
Noun

time when the sun descends behind the horizon.

visible light spectrum
Noun

light and colors that can be seen by human beings.

wavelength
Noun

the distance between the crests of two waves.