Well Actually, There Is No Dark Side Of The Moon

It's not hard to see why the moon has inspired such fascination throughout the centuries. Not only does it possess an inherently mysterious aura, it can act as a canvas onto which we can project our own feelings and ideas. The moon is a non-luminous body, meaning it doesn't produce its own light. Instead, it reflects the light from the sun, which could be seen as somewhat tragic in a sense — a deadened rock only visible due to light it steals from a distant star. Or it could be seen as comforting and hopeful — a constant presence revealed by the light of the same star that gives us life.

However you feel about it, one particularly persistent myth about the moon certainly adds to the more mysterious, tragic view of our only natural satellite: the dark side of the moon. This concept has been a cultural constant for decades, but it is largely a misnomer, as there really is no "dark side of the moon" in the most literal sense. However, if you take "dark" to mean unexplored or mysterious, it's a much more appropriate descriptor. Here's why the idea of the "dark side of the moon" is a bit of a myth.

Just like Earth, the moon is illuminated by light from the sun. The star at the center of our solar system beams light towards our planet which also reflects off the surface of the moon, thereby creating moonlight. As is the case on our own planet, the moon has its own rotation and orbit, which means only certain areas of its surface are directed towards the sun at any given time, giving the moon its own day and night. In that sense there is always a "dark side of the moon" just like there is always a dark side of the Earth. 

But just as no part of Earth's surface remains in perpetual blackness, this dark side of the moon is not a fixed area. As the moon moves through its orbit and rotation it goes through phases which change how much of its surface we can see from Earth. This is why we sometimes see a full moon, sometimes a crescent, and sometimes nothing at all. 

Of course, when we use the phrase "the dark side of the moon" we're typically not referring to the part of the moon that happens to be rotated away from the sun at that particular time. We're referring to the side of the moon that is facing away from our planet which we never see. But as you might have picked up based on the fact the moon rotates just like our own planet, this is by no means a "dark" side of the moon.

The moon is in sync with the Earth in many ways, most notably in terms of being locked in a sort of gravitational dance with our planet known as tidal locking. In the time it takes for the moon to orbit Earth, it also rotates once on its axis which means we see the same side of the moon whenever we look up at the night sky. As such, it appears as though we're able to see just half of the moon from our world, but due to something called libration, we can actually see roughly 59% of the moon's surface (taking into account all of the moon's phases). Libration refers to the way in which the moon's elliptcal orbit around our planet, the tilt of its rotation, and Earth's own rotation means that over the course of the moon's orbit, we're able to see it from slightly different angles. This all adds up to around 59% of the moon's surface being visible from Earth.

That leaves 41% of the moon which we never see, and it's this portion of our lunar body that we typically refer to when we use the phrase "dark side of the moon." But as we know based on the fact the moon rotates just like our own planet, the side of the moon that we can't see gets as much sunlight as the rest of the surface, and experiences the lunar equivalent of days and nights just like Earth (though a full day to night cycle on the moon takes roughly 29.5 Earth days). As such, a better name for the portion of the moon we can't see is "the far side of the moon."

Over centuries, humankind has become acquainted with the 59% of the moon visible from Earth's surface. It wasn't until 1959 when we got our first glimpse of the other side courtesy of the Soviet Union, which launched the Luna 3 spacecraft that year and took the very first picture of the "dark side of the moon" on October 7, 1959.

Though it wasn't the sharpest shot of this mysterious hemisphere, it was a historic moment that revealed a part of our Earth–moon system that had remained hidden for billions of years. What's more, it revealed that the far side of the moon looks a lot different to the side facing Earth. The hemisphere pointing away from our planet only has a few dark spots, whereas the side we see has many more dark patches. These are caused by a material called lunar mare, ancient lava which erupted into craters caused by impacts from other celestial bodies hitting the moon.

In the years since the Luna 3 image was captured, scientists have tried to explain this difference, and in 2023, a study published in the journal Science Advances provided the best attempt yet. Researchers showed that an impact which formed the moon's largest impact basin, the South Pole–Aitken, also caused heat to radiate through the moon's interior, which in turn carried an array of materials to the moon's nearside, thereby contributing to the volcanic activity that ultimately caused more eruptions on the moon's nearside. This is why the side we see looks darker than the far side, which ironically means that the side with which we're more familiar is actually more accurately described as "the dark side of the moon" than the hemisphere we don't see.