Why Is the Sky Red at Sunset?

What You'll Learn

• Sunlight looks white but is made of all rainbow colors
• Light travels in a straight line until it bumps into particles in the air
• Shorter colors like blue and violet scatter more easily than longer colors like red and orange
• At sunset, sunlight travels through more atmosphere, so most blue light scatters away
• The remaining red and orange light reaches our eyes, making the sky look red

Words to Know

Atmosphere

The layer of air and gases around Earth

"Light travels through the atmosphere."

Scatter

When light spreads in different directions

"Blue light scatters easily in the sky."

Sunlight

Light from the sun that contains all colors

"Sunlight looks white but has rainbow colors."

Sunset

When the sun goes down in the evening

"The sky was red at sunset."

Check What You Learned

Fun Facts

• Sunlight is composed of all colors of the visible spectrum

  Source: NASA

• Rayleigh scattering: shorter wavelengths (blue/violet) scatter more strongly than longer wavelengths (red/orange) when interacting with air molecules

  Source: University of California, Berkeley

• The daytime sky appears blue because blue light scatters across the atmosphere

  Source: NASA

• At sunset, sunlight passes through more atmosphere (longer path length), scattering most shorter wavelengths out of the direct beam

  Source: NOAA

• Remaining longer wavelengths (red/orange) dominate the light reaching the observer

  Source: American Meteorological Society

• Dust, pollution, and clouds can enhance red/orange sunset colors

  Source: NASA