The far side, or dark side of the moon is the part of the moon that constantly faces away from earth. Though most people think of it as a “dark” hemisphere, this side of the moon gets as much sunlight as the side we see when the moon is full, which means the name “dark side” is used as a misnomer – that
is, unless you’re talking about the 1973 Pink Floyd album.
This far side has a rugged terrain filled with scores of craters; including one of the largest in the solar system, the Aitken basin. The entire moon experiences two full weeks of sunlight, followed by another two weeks of night; and perhaps you know this already, but portions of the dark side are gradually slipping into view.
What exactly is this “Dark Side” of the moon?
To understand the moon completely, we must first describe what causes one half of this satellite to remain forever facing away from our planet. When viewing the moon from earth, it appears as if it doesn’t turn, but in fact, the moon is turning all the time.
It turns on its own axis and loops around the earth at the same rate, and this is why astronomers say the moon is “tidally locked” to earth.
But our satellite wasn’t always like this. Astronomers believe that our moon, like other natural satellites, initially span at a much faster rate, and has been influenced by the earth’s gravitational pull.
The earth exerts torque on protrusions in the lunar surface, causing its rotation to synchronize with its orbit – and this same phenomenon can be seen with lunar surfaces on other planets including Saturn and Jupiter.
The moon experiences strong tidal forces that slow its rotation and keep one side facing away from earth, however, close to 60 percent of the entire moon’s surface can be seen from earth, through the aid of astronomy binoculars and telescopes.
Tidal locking is the reason people watching from earth’s surface don’t have a clue what the moon’s far side looks like. But we did get a glimpse into the dark side when in 1959 the Soviet space probe named Luna 3 took pictures of a vast, crater-dense landscape that few people have ever seen with the naked eye.
Is the dark side different from the side we see from earth?
The moon’s two hemispheres show major differences in appearance, with the near side covered mostly with maria (large lunar surfaces) that early astronomers initially identified as seas.
The far side takes on a more cratered appearance with fewer maria (just 1% compared to about 30% on the near-side) and this is attributed to a lower presence of unique elements on the dark side.
The people who first laid eyes on the dark side were astronauts in the Apollo 8 mission in the late 1960s, as their space craft orbited the moon before landing.
So the dark side isn’t really dark, except in the sense that people don’t know much about it. It is believed that differences between these two hemispheres are a result of a large collision perhaps from a smaller moon that may have also have come from the Theia collision.
Until in the late 50s, one half of the moon remained a mystery and even after the first pictures emerged and Apollo 8 landed on the surface, for a long time there has been a sort of mystique about what really goes on up there.
Moon librations are the reason we see a little more of the far side than we did decades ago. Before space explorers employed advanced technology to view the surface of the moon, they expected the far side to look the same as the visible side.
The general public held the same assumptions, but this of course changed when the Russian Academy of Sciences printed a catalogue of 500 pictures of the far side, showing humongous craters and other distinguishing features.
Transmission and Communication
The unseen side of the moon shields electronic transmission (radio waves) from the earth, making it communication a challenge if a space vessel is stuck on that side.
Astronauts from the Apollo missions all had to break contact with space command for a short time until the space craft circled back to the front or near side of the moon, and this created some tense moments during those early flights.
Because this far side is completely shielded from earth’s radio waves, some believe it’s a good location to set up radio telescopes such that can be used to advance communication during missions. The craters are shaped like bowls and provide a great formation to set up a stationary telescope.
There are challenges though: for instance, the fine lunar dust can easily damage equipment, vehicles, and even space suits.
Also, any equipment placed here must be shielded from powerful solar flares, and the entire area where such telescopes would be placed must also be shielded from other radio sources so that signals aren’t contaminated.
Conspiracy Theories and Myths
Conspiracy theories abound as to the possibility of underground bases, alien bases, alien technology and large “castles” that are believed to exist on the far side of the moon. UFO conspiracy theories are unsubstantiated and have been rejected by NASA.
The truth is you don’t need to board a powerful space craft to catch a glimpse of the far side. While it’s true that only half of the entire surface is visible at any time, it is possible to catch smidges of the concealed surface as they are constantly revealing themselves to keen observers.
This is why throughout a lunar cycle, observers on earth can see 50% of the moon surface, provided they know where to look.
The moon wobbles along its orbit…
The moon’s position is constantly shifting relative to the earth and the sun, and as darkness moves to envelop one side and recede from the other, we also get to see something else about our satellite; it tends to wobble on its course.
The experts call it wobble librations, and they are triggered by the moon’s elliptical orbit and the orientation of its axis. When viewed from earth, the moon has a tilt (relative to its axis) that makes it look as if it is delivering a nod to observers here.
Furthermore, the eccentricity of its orbit allows observers to see the north and south poles, as well as its eastern and western edges as it goes on swishing through its orbit. The moon’s tilt also shows us huge patches of the surface that are indeed, always dark.
Now, this doesn’t lend weight to the term “dark side”; instead, it means there are huge craters that never see light, at least not from our sun.
How to view the moon from earth?
If you love watching the moon with your naked eyes, you’ll love using a telescope even more. The detail you get of mountains, valleys, and craters, is phenomenal – it basically opens up a new world. But like any tourist, you need a good moon map so you know what to look for.
When using moon maps, you can use either a normal map or a mirror-reversed version, but the latter is normally used by people with refractors and/or cassegrain telescopes, which are designed to shift the moon’s image from left to right.
So when’s the best time to check out the moon?
You might think it’s during the full moon, but this is actually the worst time to do this. On a full moon light rays from the sun hit the surface straight overhead, much like what a desert looks like at high noon.
So the best time to observe the moon’s surface is actually during the “quarters”, when the moon is only a quarter through its orbit, and is getting sunlight from left or right.
Tips on observing the moon
Always focus on the terminator, the boundary between dark and light. Bear in mind that the sun rises along this line, and so you will have to watch out for the shadows.
As a matter of fact, if you observe the surface for a while, you will start to pick out the shadows and watch as they move with the sun.
As light hits the surface from different angles, it sets out all sorts of shadows on the moon, which you will get used to and start mapping out as you get a clear picture of the landscape.
Beginners are often surprised at how bright the moon is when viewed with a telescopes. But actually, it doesn’t get any brighter than an asphalt highway when exposed to the bright sun on a blue sky. The reason it looks so much brighter is that you’re viewing it from dark location in a dark sky.
If you find it a bit too bright, consider turning on the lights in your room (or wherever you’re viewing from) or start observing the moon before the sky is completely dark.
As the full moon approaches, it becomes more challenging to see details, and our satellite becomes a washout, though it’s still great for romantic evenings. After the full moon, viewers can pick up their telescopes again – but this is where many people start to lose the moon.
It happens because the moon rises 50 minutes later every evening, and by the time it gets to third quarter, it rises at midnight, rising up high in the southern sky.
But of course, if you don’t mind staying up late to gaze at the moon, this shouldn’t be a problem for you. If you can’t stay up late, there’s no problem; you can still observe the moon during this time, but you’ll have to wake up early in the morning.
Don’t hold back here, in fact, there’s no good and bad magnification when viewing the moon – so try all of them. To see the whole moon you will need a lower magnification; basically a way to grasp the “big picture”.
But to see the beauty of the moon, you will need a higher magnification, perhaps 150x. Keep in mind the moon tolerates higher magnification than any other object you can view in the sky, and this means you won’t hurt your eyes from being exposed to glare.
If the moon is rising, don’t use high magnification then, because it won’t be as effective. The same goes for when the moon is setting. That’s because at this stage the moon appears too close to the horizon, with a sort of blurry haze that makes it look like its boiling.
Get a moon maps and atlases and start identifying craters down the terminator. How many craters can you identify? Note the varying sizes, the shapes, floors, and whatever other topographic features area there.
Moon Landing Sites
Some things on the moon you almost never see here on earth. These include rilles, or grooves that appear on the surface, and are believed to be what’s left of collapsed lava tubes.
Other strange structures include domes, and “seas”, or vast lunar surfaces that are perfectly flat. From your observation room you can identify Apollo landing sites – you won’t see any of the stuff they left behind, but if you pay close attention you can identify the landscape.
Take as many pictures are you can. The moon is properly lit by our sun, so it’s fairly easy to take good pictures if you hold your camera or cell phone to the telescope’s eyepiece.
For more exquisite photos I recommend purchasing a decent telephoto lens for your DSLR camera. Astronauts Harrison Schmidt and Gene Hackman landed in the highlands of Taurus-Littrow, on an afternoon in December 11, 1972.
According to the mission timeline, they deployed the flag and spent about an hour exploring.
These bits of information come to light when you can pinpoint where on the moon it happened, and it gives the observer a sense of pride and awe, that some among us have been there and came back.
If you’re a big fan of the moon, there are interesting groups that you can join and share your experiences with other amazing people all over the world.
Well I hope you’ve enjoyed this article, “What is the dark side of the moon?”, and have found it useful. If you did, consider checking out my other articles that are full of equally good tips and tricks for everything amateur astronomy and stargazing. You’ll find them here:
- How To Find The North Star?
- Astronomy Telescope Types
- Does The Sun Rotate?
- Does Saturn Have Clouds?
- How Far is Mars from Earth? Facts About Mars
- What Causes the Northern Lights?
- Top 10 Small Telescope and Binocular Objects
- Best Kids Telescope for Viewing Planets
- How To Clean Telescope Lenses – 5 Simple Steps
- 10 Tips For Buying Your First Telescope
- Best Binoculars For Astronomy Beginners
- Best Binoculars For Astronomy Under $500