Why Does the Moon Appear Orange Sometimes?
Moonlight, before it reaches our eyes, passes through the Earth’s atmosphere. As the light travels through the dusty air, its different colors are scattered. The air scatters the violet and blue rays of light more than it does the reds and yellows.
When the moon is near the horizon, its light must travel through much more air to reach the viewer than it does when the moon is overhead. If the air is particularly dirty when the moon is low, the blue and green colors in moonlight are soon filtered out, leaving more reds and yellows for us to see, and the moon looks orange.
Although it seems to change colors, the Moon itself stays the same color year-round. The different colors we see from time to time are the result of our particular viewing angle, along with the composition of Earth’s atmosphere.
These atmospheric particles tend to scatter shorter wavelengths of light more than longer wavelengths. Orange and red light, which have longer wavelengths, tend to pass through the atmosphere, while shorter wavelengths of light, such as blue, get scattered.
That’s why the Moon — and the Sun! — look orange or red when they’re rising or setting. If you’ve ever seen an orange Moon high in the sky, the atmosphere is still the reason it’s orange.