The moon has long captured our imaginations. It’s embedded deep in mythology around the world, and even became the first calendar for many ancient people. But our connection to the moon goes even deeper — its symbiotic relationship with the planet Earth is unique within the solar system, and without it, we might not even exist. These 10 facts about our nearest lunar neighbor just might deepen your appreciation for Earth’s one and only natural satellite.
The Moon Is Bigger Than Pluto
If you were in grade school before 2006, when the International Astronomical Union reclassified Pluto, you may still think of it as a full-fledged planet. While the classification isn’t, technically, entirely about size, it’s hard to overstate just how itty-bitty Pluto is. Its radius is only about 715 miles, compared to a mean radius for the moon of about 1,080 miles.
Some other moons even outrank full-fledged planets, size-wise. Our solar system’s two largest moons, Jupiter’s Ganymede and Saturn’s Titan, are both larger than Mercury!
The Moon Is 27% the Size of Earth
While Earth’s moon is only the fifth-largest moon in the solar system, everything changes when we grade on a curve: At more than a quarter the size of Earth, our moon is, by far, the biggest when compared to its planet. According to NASA, if the Earth were a nickel, the moon would be the size of a coffee bean.
This gives our moon an outsize influence on our planet compared to others, in ways that almost seem magic — but are very much real.
The Moon Causes the Tides to Change
Not only does the moon influence the tides, but we wouldn’t even have tides without the moon. Its gravitational pull tugs up the water on the sides of the Earth facing and opposite the moon. This action is called tidal force. The moon’s gravity also affects land, but not nearly as much as water.
Forces besides the moon influence tidal patterns, too. Since the Earth isn’t entirely covered in water, land masses can affect how dramatic the tides get. The sun can have its own effects on tides, too, although it’s not as noticeable until the sun, moon, and Earth line up for a new moon or a full moon, causing tides to get much bigger.
The Moon Helps Stabilize Earth
The moon’s unique relationship with the Earth, it turns out, is crucial for preventing and slowing major, deadly climate shifts — at least the naturally occurring ones. The moon’s large mass helps keep Earth from tilting too quickly, preventing the kind of wobbles that created dramatic climate conditions on Mars. It could be that larger moons are one of the factors a planet needs to create and sustain life.
The “Moon Is Made of Cheese” Myth Is a Millenia-Old Joke
Today, the idea of the moon being made of cheese is a deeply -embedded fanciful trope appearing in everything from children’s books to B-movies to tasty snacks. It’s central to the premise of the Wallace and Gromit cartoon “A Grand Day Out.” But where did this cutesy reference to the moon’s appearance come from?
There’s no evidence of a widespread historical belief that the moon was actually made of cheese. Its origins lie in various folktales passed down in many cultures’ oral traditions. In some, a fox tricks a wolf into believing the reflection of the moon in a well is cheese, which convinces him to dive in. In others, it’s a human simpleton who dives into the well. The Aarne-Thompson Index, a folktale classification system, even has specific listings for “the Wolf Dives Into the Water to Eat Reflected Cheese” (34) and “Diving for Cheese” (1336). Variations of these myths appear all over the world, from the Zulu Kingdom to the Scottish Highlands. Typically, the person or creature thinking the moon is cheese is the butt of the joke.
“The Moon Is Made of Green Cheese” (referring to the freshness of the cheese, not its color) evolved into a figure of speech describing an easily duped person (think “I have a bridge to sell you”) as early as 1546, when it appeared in a proverb by English writer John Heywood. The trope remained incredibly common for centuries to come.
The term has also been used as a variation of “when pigs fly,” as in German playwright Bertolt Brecht’s play Good Person of Szechwan.
The Moon Is Deeply Scarred From Asteroids and Comets
Celestial bodies crash into the moon all the time, creating its somewhat chaotic surface. Often, these meteors are the size of a speck of dust, but larger collisions are not uncommon. During the 2019 total supermoon eclipse, casual observers and professionals alike caught the tiny flash of a meteoric impact, which caused an explosion roughly equivalent to 1.7 tons of TNT.
Debris that size hits the moon roughly once a week, and NASA’s Lunar Resistance Orbiter has tracked more than two dozen new impact craters since 2009. The lunar proximity to Earth means the same stuff that’s hitting the moon is whizzing past us, too — but without an atmosphere, the moon is much more vulnerable.
Of course, the bigger scars are from bigger impacts, and we’re still seeing some of those today. In 2014, Spanish astronomers observed an 800-pound meteorite crash into the moon’s surface. Researchers with the Southwest Research Institute, University of Toronto, and University of Southampton were able to date some of the moon’s larger craters in 2019, and later created a one-minute visualization of their research with music that corresponds to each impact.
12 People Have Walked on the Moon
The most famous moonwalkers are probably the first two, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin, who made their historic mission in 1969. But that was just the first of many crewed lunar landings in the Apollo program over a three-year period. All together, 12 people have walked on the moon so far. But nobody has set foot there since Apollo 17 in 1972 — and so far, only American white men have had the opportunity.
Another 12 astronauts reached the moon without walking on it, including the crews of Apollo 8 and Apollo 10, which orbited the moon without landing. Others were on later missions, but had different tasks, like Michael Collins, who stayed in orbit 60 miles above the moon during Apollo 11, making sure they could all get home safely, while Armstrong and Aldrin went to the surface.
Scientists Think a Collision of Two Planets Created the Earth and Moon
While there are many theories regarding its origins, the most widely accepted one is that the moon arose after a protoplanet approximately the size of modern Mars crashed into the Earth about 4.5 billion years ago, knocking loose debris from both bodies that would gradually become the moon. New research (as of 2021) proposes that there were actually two impacts: one extremely fast one that knocked the material away, and another slower one that helped merge the debris.
The Moon Is Darker-Looking on the Earth Side
You’ve heard the phrase “the dark side of the moon,” referring to the side that’s not facing Earth. Technically, the sun shines on both sides of the moon — but the majority of those dark, mottled patches — actually expanses of solidified lava called lunar seas, or maria — are on the near side. At more than 1,600 miles wide, Oceanus Procellarum, or Ocean of Storms, on the western edge of the near moon, is the largest of them all.
These vast plains of basalt come from volcanic activity, but the exact mechanism of their formation is still being studied. Some were created or at least helped along by asteroid impacts, but that’s not the whole story either, since similar hits typically don’t get the same reaction on the far side.
This isn’t to say that the far side is pristine. It’s heavily pockmarked with impact craters.
The Man in the Moon Comes From Lunar Seas
There are many lunar seas smaller than the Ocean of Storms, and several of these, along with brighter lunar highlands, make up the face that some people in the Northern Hemisphere see on the surface of the full moon.
Your mileage may vary depending on where you live and how your brain sees things, but usually the Mare Serenitatis (Sea of Serenity) is one of the eyes. The other eye is formed by the Mare Imbrium, or Sea of Showers, immediately to the west.
The nose, appropriately, is not a mare, but a sinus, or bay: Sinus Aestuum, or Bay of Seething. The mouth, which is open to interpretation but sometimes described as “grinning,” is a combination of Mare Nubium (Sea of Clouds) and Mare Cognitum (Sea That Has Become Known). In the Southern Hemisphere, the moon is flipped vertically, and many people see the Northern Hemisphere “face” as a rabbit. But some see a more joyful little face, too: Mare Frigoris, or Sea of Cold, could be seen as a much more defined grin.