The moon has been obsessed over by poets and scientists alike for centuries. When you see a harvest moon hanging low in the sky, burning with an intense orange glow, you understand why this nearby celestial is so unanimously beloved.
There seems to be an element of magic at play when this big white ball in the sky suddenly (and drastically) changes hue. This has fueled the often wild imaginations of Earth-bound onlookers.
Yet, as is the case with most things in this life, the reason for this change in color is scientific. It is due to air molecules.
That said, we imagine you came here looking for a slightly longer, more comprehensive answer than this. So let’s momentarily pop the moon under the microscope and ruminate on its technicolor transformations.
When Does The Moon Look Orange?
To get to the bottom of the multicolor moon mystery (Also check out How Many Light Years Away Is The Moon?), we should avoid asking why the moon is orange. Instead, we should focus on when the moon appears orange.
As we’re sure you’re aware, the moon isn’t actually orange. It appears as mottled white in the night sky. This means that when it appears orange, something must be causing the transformation. As it turns out, it is something specific to the time at which the transformation takes place.
So, ask yourself when you last saw an orange moon. You may not have been all that aware of the temporal aspects of your sighting. However, it was almost certainly a full moon, right?
This means that you probably noticed it because it was also big and low-hanging. Sound about right?
It should, for these are the exact conditions that facilitate an orange moon. Allow us to elaborate.
What Creates An Orange Moon?
The Earth is encapsulated by its atmosphere. Our atmosphere is a veritable cocktail of different gasses and particles. The molecules and particles within this cocktail refuse to let light through without a fight.
As light passes through the atmosphere some of the light’s color frequencies are scattered or absorbed by the atmospheric matter. This prevents them from reaching the Earth, and of course, our eyes.
One frequency that isn’t effectively scattered by these meddling molecules is, you’ve guessed it, orange. More accurately, it is the longer wavelengths of light that are scattered less. Longer wavelengths of light also include red light.
Okay, But Why Isn’t The Moon Always Orange?
We assume you’re wondering why the moon only appears orange in certain instances. It’s a good question that we’re equipped to answer in full!
When the moon is high above us in the sky, the reflected light of the sun travels straight down (or thereabouts) towards us (Find out Why Does The Moon Shine?). It shoulders its way directly through the atmosphere head-on.
But when the moon is nearer to the horizon its light must travel horizontally through the atmosphere to reach us. This means there are significantly more molecules to contend with. As a result, the colors we’re used to seeing are scattered before the light reaches our eyes.
It’s like we’re viewing the moon through exceedingly thick, orange-tinted glasses. When the moon charts a higher course through the sky, it’s as if we’re looking at it through regular lenses or none at all!
Just to put a number to it light from the Moon on the horizon has to travel through seven times more atmosphere than when it is overhead.
Why Is It That Orange Frequencies Survive The Journey?
Okay, next on the agenda… Why orange? Light frequencies operate at different wavelengths — Some are shorter, and some are longer.
Light of shorter wavelengths is more affected by the atmosphere. There are refracted to a higher amount. Also, because the wavelengths are of a similar size as particles in the atmosphere it is more easily blocked. Conversely, longer wavelengths are not as affected by these factors.
Blue and other cold tones are short wavelengths, while the warmer orange and red tones are long wavelengths.
So, when there’s a veritable wall of atmosphere to contend with, the colder hues are weeded out. At the same time, the warmer hues make it through.
It can be hard to think of light and color in such concrete terms. We suggest using the strings of a guitar as an analogy.
The cold hues are like the bottom three thinner strings. The warmer hues are like the top three thicker strings.
The thin strings are pulled taut to produce higher notes, and the thick strings are a little looser to produce lower notes.
Now, if you pluck one of each simultaneously, you’ll notice that the thicker (lower) string has more sustain. This is because it’s looser, and thus, there is less resistance, meaning the string oscillation is much wider and slower.
By contrast, the thin (high) string pulled ever so taut across the instrument performs a narrower oscillation at higher speeds that quickly runs out of steam.
I Saw An Orange Moon High In The Sky
An orange moon will most commonly hang very low in the sky. However, it is technically possible to see an orange moon when it’s higher up in the heavens.
The reason for this is that, in certain instances, lots of air pollution is mingling with the natural atmosphere. This dramatically increases the number of particles and molecules between the moon and the Earth.
When the light tries to get through, the short wavelength frequencies are intercepted by the matter of the atmosphere. Like when the moon is close to the horizon the moon once again appears orange.
What Causes A Blood Moon?
A red blood moon is caused by similar molecular interference in the atmosphere. However, this interference coincides with a total lunar eclipse. A lunar eclipse occurs when the Earth is directly in between the sun and the moon. During a total eclipse, very little light can reach that silvery celestial.
Only a very small amount manages to refract around the Earth to the moon. As the light has to travel through the atmosphere it is refracted. As detailed earlier red light is refracted more than shorter wavelength light. It is this red light that is directed to the Moon, resulting in a Blood Moon.
Final Thoughts
And thus closes the curious case of the orange moon. By reading this article, you now know the science behind this eye-catching phenomenon. However, don’t let it detract from the magic it conjures in your imagination. Hopefully, the knowledge will deepen your connection with such an event.
There are other colors that the Moon is named after. Not all of them are due to the color that the Moon appears. For example, the full moon in April is called a Pink Moon. It is named after a pink wildflower that blooms in Spring in North America.
Hi, my name is Jason Anderson, and I am a Physics Professor. Ever since I was a kid, I’ve been fascinated with space, the universe, the moon, you name it. I spent hours and hours at the planetarium close to my hometown, wondering what else could be out in the universe.
Since then, I’ve been an avid stargazer and astronomer, and love nothing more than spending my time charting stars, observing planets, and finding constellations.
This is why I decided to start Telescope Guru. I only wish to share this fun pastime with the world. With this site, I hope to answer all of your questions relating to astronomy, telescopes, and stargazing.
