Sunset Red: Why Does the Sky Change Color at Night?

When the sun is low on the horizon at sunset, the sunlight has to travel through a much thicker layer of atmosphere to reach your eyes compared to when it is directly overhead. This long journey through the air acts like a filter, slowly removing colors one by one.

Blue and violet light are scattered away very early in this long journey through the thick air. Red, orange, and yellow light have longer, lazier waves that can travel through dense air without bumping into as many molecules. These 'survivor' colors are what's left over to reach your eyes and paint the sky in warm tones.

Sunsets get an extra boost from particles in the air like salt from the ocean, dust from deserts, or even volcanic ash. These larger particles help reflect the red light toward you. If there are high clouds in the sky, they act like giant movie screens, catching the red rays and making the whole sky look like it’s on fire.