One thing about me that you can always expect to hear during the dark of night is ‘look at the moon!’ There’s something about that brilliant white light shining in the sky that is so beautiful to me. However, why does the Moon shine?
And I find it hard to believe that everyone does not feel the same.
There’s something just so stunning about it. I heard an old story once saying that the sun loved the moon so much that he’d die every night just to allow her to breathe.
And it really stuck with me. Maybe that’s why the idea of dancing in the moonlight is so romantic?
And while that may just be an old folks tale, there’s definitely some truth in it. The sun and the moon are forever bound and linked in a never-ending dance. Of course, the sun does not die during the dark of night, we know this.
But the Sun is responsible for the gorgeous glow of the moon that we’ve come to know and love. Want to learn more about how and why the moon shines? Then keep reading on.
Does The Moon Shine By Itself?
It’s a fair question to ask or an assumption to make, right? That the moon produces its own light? You only have to look up at the dark sky to see it shining brightly.
But it’s not actually the case.
You see, the moon is essentially just a rock. There’s a bit of anorthosite mixed in with some dark and hardened basalt lava too. As such it is actually a dark-colored rock.
You likely don’t recognize the names of these rocks and that’s because they don’t really have any interesting or special characteristics. And that includes light.
Just as you won’t see rocks on Earth emitting light, this big old floating rock in the sky does not produce light either. In fact, there are no properties on the moon at all that are even remotely responsible for the production of light.
So where does the light come from then? Let’s find out.
If It’s Not The Moon Itself, What Does Cause The Light?
Our celestial neighbor, the sun, is the actual cause of light from the moon. And without it, we’d never actually see the moon (Also check out Why Is The Moon Orange?). And how sad would that be?
Just like the sun produces all the light for us humans, and aliens if they’re out there (?), it too illuminates the moon to allow it to be visible to the naked eye.
You see, the light is actually just reflected from the moon’s surface, which then cascades down towards our planet.
Imagine the moon like a mirror. The light from the sun bounces off it and then comes down towards the earth.
How Does A Rock Reflect Light? It’s Not The Best Mirror
This is where things start to get a little more complicated. After all, how many rocks do you see on Earth that reflect light like a mirror? It’s not many. Have you ever seen a rock do this at all? I haven’t.
So how does the moon manage it?
Well, pretty much everything in the solar system either emits or reflects light. Things are a little different in space than down here on Earth. And the moon is one of the many that fall into the latter category.
While from down here it looks like a brilliant white light (You might also want to check out What Is A Spectroscope Used For?), the surface of the moon is actually pretty dark. Because of the moon’s lack of a discernible atmosphere, it’s really susceptible to the impact of any foreign objects.
This means that it has lots of craters, mountains, trenches, and even volcanic remains. So, it’s a bit more like a very faded, bumpy, uneven mirror.
This means that even though it’s reflective, it’s actually not all that reflective. If the surface were smoother, we’d have an even brighter moon during the night.
And this uneven surface can contribute to why the different phases of the moon can be brighter than others.
Brightness & The Phases Of The Moon
The moon is always at its brightest and most dazzling during a full moon, and as the rock in the sky seems to get considerably smaller, it’s because there are areas of the moon that are becoming incredibly dark. It may surprise you to learn that that surface of the Moon is about as reflective as coal.
Since the light of the moon comes from the sun, the moon’s location in accordance with the sun is what actually creates the different phases.
The moon always looks as it does during a full moon. It’s not as if the moon shrinks or grows in size. It’s just how much of the sun’s light is reflecting off it at different angles throughout the year.
Just as the Moon displays phases when viewed from Earth the Earth displays phases when viewed from Moon.
How Bright Is The Moon Compared To The Sun?
The way that brightness in the sky is calculated can get a little tricky. Essentially, it is calculated by evaluating the magnitude.
But to make things a little simpler, let’s put it this way, for the scale that is used to measure brightness, the lower the value the brighter the object is.
So the sun comes in at -26.7 as the brightest object we can see by a long mile. Its light is so bright that besides the moon it drowns out all other objects in the sky. The moon comes in at around -12.7.
To put this into perspective, the sun is 398,100 times brighter than our moon. So, that’s the number of moons you’d need in the sky to see as much light as you do from the sun during the day.
This explicitly shows us just how much brighter the sun is than the moon. And remember, all the brightness of the moon actually comes from the sun anyway. Without it, we wouldn’t see the moon at all.
Final Thoughts
The two biggest sources of life for the Earth are definitely the sun and the moon. And while it might not quite be the case that the sun dies each night to give the moon its time to shine, the sun and the moon will always be connected.
Without that shining star in the sky, we would never be able to see such a beautiful sight in our dark skies.
The most accepted model for the formation is that the Earth was hit with a Mar-sized planet early in the Planet’s history. The collision resulted in a lump of material coalescing to form the Moon.
Why do we only see one side of the Moon?
We do not see the far side of the Moon because it is widely locked to Earth. The masses of Earth and Moon result in a dynamic caused by gravity that makes one side face us at all times. Because this is not a perfect situation the Moon ‘woobles’ a little allowing us to see 59% of the Moon. However, at any one time, we can only see 50% of it.
Is the Moon always the same size?
No, the Moon is not always the same size. This is because the Moon is closer to us than at other times. At its largest, the Moon is 14% larger than when it is at its smallest.
Why can we sometimes see the dark area of the Moon dimly lit?
When the Moon is a small crescent it is possible to see the dark areas dimly lit. This is because light is reflected by the Earth, and it lights the Moon’s sky in the same way that the Moon lights the Earth’s sky. Some of that light is reflected back to Earth. This reflected light is called Earthshine.
Is there evidence that the light from the Moon is reflected light from the Sun?
Yes, there is. By studying the nature of the light we can determine that it originated from the Sun. Any body emitting light leaves a fingerprint in the light. Spectrographic analysis of the light from the Moon has the Sun’s fingerprints in it. A fun project is to map the positions of the Moon and Sun over a complete lunar Moon. If you study it closely you will learn a lot about orbital mechanics and the phases of the Moon while proving to yourself that the Moon reflects the Sun’s light.
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.
