Have you ever seen the moon turn a beautiful or scary orange, or even an orange-red color? Did you ever wonder why this occurs? This lesson explains why it sometimes looks white and why other times it looks orange.
Sunrise and Sunset
Do you enjoy watching a sunrise? One very distinct thing you’ll notice every time you see one is that the sun and the surrounding clouds, if any, appear quite orange and even red. Then, as the sun rises higher up over the horizon, it turns yellow and then a blazing white.
As it falls back toward the horizon, it turns orange and red again as it sets. Do you know why this occurs? If you do, then you already know why the moon turns orange. If you don’t, then you just got a big clue as to why the moon can turn as orange as the sun during sunrise or sunset.
Wavelengths of Light and the Moon
To understand why the moon can appear white or orange at different times, we need to understand some very basic things. The first thing is this: The moon doesn’t generate any visible light. It only reflects the sun’s light onto our planet.
Think of the moon as a mirror rather than a flashlight. The flashlight, our sun, shines onto the surface of the moon, and the moon reflects this light onto the Earth. That’s why we can see the moon!The light that bounces off of the moon typically appears white because, despite being called a yellow dwarf star, the sun actually emits a color that appears white when seen from outer space, with the highest output of visible light occurring in the green portion of the color spectrum.That white color is really a mixture of many colors and each of those colors has a specific wavelength.
If you looked at the spectrum of visible light, you’d see that longer wavelengths of visible light tend to have orange-red colors while shorter wavelengths of light tend to have bluish colors.
Why the Moon Turns Orange
With those technical details out of the way, you can now start to understand why the moon turns orange. One key thing we mentioned a second ago is that the sun is actually white when seen from outer space, but it has a yellowish tint to it many times of the day when seen from Earth. Why? That’s because outer space doesn’t have an atmosphere. Our Earth, however, has an atmosphere that acts like a filter. In this case it doesn’t filter water, it filters particular wavelengths of light.Longer wavelengths of light like orange and red can penetrate our atmosphere much farther than shorter wavelengths of light, such as blue; which are scattered.
Ergo, when the moon is overhead, the light it reflects doesn’t have to penetrate as much of our atmosphere compared to when it’s nearer to the horizon. Meaning, when it’s overhead, it appears whiter because more of its colors reach our eyes.
However, when the moon is nearer to the horizon, its light has to pass through more of our atmosphere than when it’s overhead.
This means colors like blue are scattered away even more so than before, while orange and red still reach our eyes. This causes the moon to appear orange when it’s still very much white when seen from outer space at the same exact time.
This means that you’ll notice that when the moon is orange, it’s nearer to the horizon. When its whiter, it’ll be more overhead.
Now, there is an exception. Maybe you have seen the moon turn orange when it wasn’t near the horizon. What could explain that? Well, anything that acts like a filter for light can cause it to turn orange, it doesn’t just have to be our normal atmosphere. Smoke from forest fires and pollution from our cities can all rise up into the air and act like a filter. Both will scatter away the blue light and allow the orange and red parts of the moon’s light to reach our eyes, turning it orange even when it’s not near the horizon.
So, you see, the reason our moon turns orange has nothing to do with the sun being orange or the moon emitting only an orange light. It has everything to do with the Earth’s atmosphere.
The sun gives off a light that appears white to our eyes when seen from outer space. This light is reflected by the moon towards the Earth. When this light has to pass through more of our atmosphere; which is when the moon is nearer the horizon, lots of blue light is scattered away and mainly orange and red light reach our eyes. This is because our atmosphere easily scatters away shorter wavelengths of light (like blue). Longer wavelengths or light, such as orange, can more easily penetrate even a thicker atmosphere.