Why is the Moon Orange or Red Tonight?
Exploring the fascinating atmospheric science behind the moon's dramatic color transformations
When you see the moon appearing orange, pink, or red near the horizon, you're witnessing a fascinating effect called "atmospheric scattering." This is the same phenomenon that causes the sun to appear vibrantly colored during sunrise or sunset.
Rayleigh Scattering Effect
Earth's atmosphere is filled with tiny particles, mainly nitrogen and oxygen molecules. When light from the sun, reflected by the moon, passes through this atmosphere, it collides with these particles.
Light is composed of a spectrum of different colors (wavelengths). Shorter wavelengths like blue and violet light are scattered much more easily by atmospheric particles than longer wavelengths like red and orange light. This phenomenon is called Rayleigh scattering.
The Moon's Position in the Sky Matters
When the moon is near the horizon (during moonrise or moonset), its light must travel through much more atmosphere to reach your eyes than when the moon is directly overhead. This means the light encounters many more particles that can scatter it.
Since most of the blue and green light gets scattered away, what remains is predominantly the red and orange portion of the spectrum. This is why the moon takes on those warm hues.
The Effect of Dust and Pollution
Dust, smoke, or pollution particles in the air can enhance this effect. These larger particles can scatter even more light, making the moon appear an even deeper shade of red.