There are a lot of unique museums in the world—the Icelandic Phallological Museum, the Beijing Tap Water Museum, the National Mustard Museum—but only one devoted to rocks that look like human faces. Found in Chichibu, Japan, about 60 miles northwest of Tokyo, Chinsekikan is run by the devoted Yoshiko Hayama, who carries on her father's tradition of searching the nearby river for rocks that resemble celebrities (she's got Elvis Presley and Johnny Depp), sumo wrestlers, comedians, and occasionally just regular people with goofy mugs. Great Big Story recently travelled to Chichibu to learn more about Yoshiko and her extremely unique establishment, as well as the criteria she uses for her finds ("It's better if there is a nose, but it's rare").
Earth as captured from near the lunar horizon by the Lunar Reconnaissance Orbiter in 2015.
On March 24, 2018, flat-earther Mike Hughes set out prove that the Earth is shaped like a Frisbee. The plan: Strap himself to a homemade steam-powered rocket and launch 52 miles into sky above California’s Mojave Desert, where he'd see Earth's shape with his own eyes.
It didn't matter that astronauts like John Glenn and Neil Armstrong had been to space and verified that the Earth is round; Hughes didn't believe them. According to The Washington Post, Hughes thought they were "merely paid actors performing in front of a computer-generated image of a round globe."
The attempt, ultimately, was a flop. He fell back to Earth with minor injuries after reaching 1875 feet—not even as high as the tip of One World Trade Center. For the cost of his rocket stunt ($20,000), Hughes could have easily flown around the world on a commercial airliner at 35,000 feet.
Hughes isn't alone in his misguided belief: Remarkably, thousands of years after the ancient Greeks proved our planet is a sphere, the flat-Earth movement seems to be gaining momentum. "Theories" abound on YouTube, and the flat-Earth Facebook page has some 194,000 followers.
Of course, the Earth isn't flat. It's a sphere. There is zero doubt about this fact in the real, round world. To say the evidence is overwhelming is an understatement.
HOT SPINNING BODIES
Not every celestial body is a sphere, but round objects are common in the universe: In addition to Earth and all other known large planets, stars and bigger moons are also ball-shaped. These objects, and billions of others, have the same shape because of gravity, which pulls everything toward everything else. All of that pulling makes an object as compact as it can be, and nothing is more compact than a sphere. Say, for example, you have a sphere of modeling clay that is exactly 10 inches in diameter. No part of the mass is more than 5 inches from the center. That's not the case with any other shape—some part of the material will be more than 5 inches from the center of the mass. A sphere is the smallest option.
Today the Earth is mostly solid with a liquid outer core, but when the planet was forming, some 4.5 billion years ago, it was very hot and behaved like more like a fluid—and was subject to the squishing effects of gravity.
And yet, the Earth isn't a perfect sphere; it bulges slightly at the equator. "Over a long time-scale, the Earth acts like a highly viscous fluid," says Surendra Adhikari, a geophysicist at the Jet Propulsion Laboratory in Pasadena, California. The Earth has been spinning since it was formed, and "if you have a spinning fluid, it will bulge out due to centrifugal forces." You can see evidence for this at the equator, where the Earth's diameter is 7926 miles—27 miles larger than at the poles (7899 miles). The difference is tiny—just one-third of 1 percent.
THE SHADOW KNOWS
The ancient Greeks figured out that Earth was a sphere 2300 years ago by observing the planet's curved shadow during a lunar eclipse, when the Earth passes between the Sun and the Moon. Some flat-Earth believers claim the world is shaped like a disk, perhaps with a wall of ice along the outer rim. (Why no one has ever seen this supposed wall, let alone crashed into it, remains unexplained.) Wouldn't a disk-shaped Earth also cast a round shadow? Well, it would depend on the orientation of the disk. If sunlight just happened to hit the disk face-on, it would have a round shadow. But if light hit the disk edge-on, the shadow would be a thin, straight line. And if the light fell at an oblique angle, the shadow would be a football–shaped ellipse. We know the Earth is spinning, so it can't present one side toward the Sun time after time. What we observe during lunar eclipses is that the planet's shadow is always round, so its shape has to be spherical.
The ancient Greeks also knew Earth's size, which they determined using the Earth's shape. In the 2nd century BCE, a thinker named Eratosthenes read that on a certain day, the people of Syene, in southern Egypt, reported seeing the Sun directly overhead at noon. But in Alexandria, in northern Egypt, on that same day at the same time, Eratosthenes had observed the Sun being several degrees away from overhead. If the Earth were flat, that would be impossible: The Sun would have to be the same height in the sky for observers everywhere, at each moment in time. By measuring the size of this angle, and knowing the distance between the two cities, Eratosthenes was able to calculate the Earth's diameter, coming up with a value within about 15 percent of the modern figure.
And when Columbus set sail from Spain in 1492, the question wasn't "Would he fall off the edge of the world?"—educated people knew the Earth was round—but rather, how long a westward voyage from Europe to Asia would take, and whether any new continents might be found along the way. During the Age of Exploration, European sailors noticed that, as they sailed south, "new" constellations came into view—stars that could never be seen from their home latitudes. If the world were flat, the same constellations would be visible from everywhere on the Earth's surface.
Finally, in 1522, Ferdinand Magellan's crew became the first people to circle the globe. Like Columbus, Magellan also set off from Spain, in 1519, heading west—and kept generally going west for the next three years. The expedition wound up back at the starting point (though without Magellan, who was killed during a battle in the Philippines). And speaking of ships and seafaring: One only needs to watch a tall ship sailing away from port to see that its hull disappears before the top of its mast. That happens because the ship is traveling along a curved surface; if the Earth were flat, the ship would just appear smaller and smaller, without any part of it slipping below the horizon.
THE EVIDENCE IS ALL AROUND (AND ALL ROUND)
But you don't need a ship to verify the Earth's shape. When the Sun is rising in, say, Moscow, it's setting in Los Angeles; when it's the middle of the night in New Delhi, the Sun is shining high in the sky in Chicago. These differences occur because the globe is constantly spinning, completing one revolution per day. If the Earth were flat, it would be daytime everywhere at once, followed by nighttime everywhere at once.
You also experience the Earth's roundness every time you take a long-distance flight. Jetliners fly along the shortest path between any two cities. "We use flight paths that are calculated on the basis of the Earth being round," Adhikari says. Imagine a flight from New York to Sydney: It would typically head northwest, toward Alaska, then southwest toward Australia. On the map provided in your airline's in-flight magazine, that might look like a peculiar path. But wrap a piece of string around a globe, and you'll see that it’s the shortest possible route.
"If the Earth were flat," Adhikari says, "the trajectory would be completely different." How different depends on which way the globe is sliced into a flattened map, but if it looked like it does on a Mercator-projection map, it might head east and pass over Africa.
Engineers and architects also take the Earth's curvature into account when building large structures. A good example is the towers that support long suspension bridges such as the Verrazano Narrows bridge in New York City. Its towers are slightly out of parallel with each other, the tops being more than 1.5 inches further apart than their bases. If the Earth were flat, the bottom of the towers would be separated by the exact same distance as the top of the towers; the planet's curvature forces the tops of the towers apart.
And for the last half-century, we've had eyewitness and photographic proof of the Earth's shape. In December 1968, the crew of Apollo 8 left Earth for the Moon. When they looked out of the Command Module windows, they saw a blue-and-white marble suspended against the blackness of space. On Christmas Eve, lunar module pilot William Anders snapped the famous "Earthrise" photograph. It gave us an awe-inspiring perspective of our round planet that was unprecedented in human history—but it wasn't a surprise to anyone.
The Roman dodecahedron Brian Campbell found in East London
One August day in 1987, Brian Campbell was refilling the hole left by a tree stump in his yard in Romford, East London, when his shovel struck something metal. He leaned down and pulled the object from the soil, wondering at its strange shape. The object was small—smaller than a tennis ball—and caked with heavy clay. “My first impressions," Campbell tells Mental Floss, "were it was beautifully and skillfully made … probably by a blacksmith as a measuring tool of sorts.”
Campbell placed the artifact on his kitchen windowsill, where it sat for the next 10 or so years. Then, he visited the Roman fort and archaeological park in Saalburg, Germany—and there, in a glass display case, was an almost identical object. He realized that his garden surprise was a Roman dodecahedron: a 12-sided metal mystery that has baffled archaeologists for centuries. Although dozens, and perhaps hundreds, of explanations have been offered to account for the dodecahedrons, no one is certain just what they were used for.
AN ANCIENT PUZZLE
A dodecahedron at the Saalburg Roman Fort Archaeological Park
Rüdiger Schwartz/Saalburg Roman Fort Archaeological Park
The first Roman dodecahedron to intrigue archaeologists was found almost 300 years ago, buried in a field in the English countryside along with some ancient coins. "A piece of mixed metal, or ancient brass, consisting of 12 equal sides," read the description of the egg-sized object when it was presented to the Society of Antiquaries in London in 1739. The 12 faces had "an equal number of perforations within them, all of unequal diameters, but opposite to one another … every faceing had a knobb or little ball fixed to it." The antiquarians were flummoxed by the finely crafted metal shell, and what its purpose may have been.
The 1739 dodecahedron was far from the last discovery of its kind. More than 100 similar objects have since been found at dozens of sites across northern Europe dating to around the 1st to 5th centuries CE. Ranging in size from about a golf ball to a bit larger than a baseball, each one has 12 equally sized faces, and each face has a hole of varying diameter. The objects themselves are all hollow.
By the mid-19th century, as more were found, the objects became known to archaeologists as dodecahedrons, from the Greek for “12 faces.” They're on display today in dozens of museums and archaeological collections throughout Europe, although given how little is known about them, their explanatory labels tend to be brief.
What's more, they have no paper trail. Historians have found no written documentation of the dodecahedrons in any historical sources. That void has encouraged dozens of competing, and sometimes colorful, theories about their purpose, from military banner ornaments to candleholders to props used in magic spells. The obvious craftsmanship that went into them—at a time when metal objects were expensive and difficult to make—has prompted many researchers to argue they were valuable, an idea that's supported by the fact that several have been found stashed away with Roman-era coins. But that still doesn't explain why they were made.
ARMED AND DANGEROUS?
A Roman cavalry charge, from the Arch of Constantine in Rome, circa 315 CE
Hulton Archive/Getty Images
In the 19th century, some antiquarians favored the theory that the dodecahedrons were a type of weapon—perhaps the head of a mace (a type of club with a heavy head), or a metal bullet for a hand-held sling. But as other scholars later pointed out, even the largest of the dodecahedrons are too light to inflict much damage. Moreover, Roman soldiers usually fired solid lead balls from their slings—nothing that looked like the intricate, and hollow, dodecahedrons.
Yet weapons aren't the only items useful in a war. Amelia Sparavigna, a physicist at Italy’s Politecnico di Torino, thinks the dodecahedrons were used by the Roman military as a type of rangefinder. In research published on the online repository arXiv in 2012, Sparavigna argued that they could have been used to calculate the distance to an object of known size (such as a military banner or an artillery weapon) by looking through pairs of the dodecahedrons' differently sized holes, until the object and the edges of the two circles in the dodecahedron aligned. Theoretically, only one set of holes for a given distance would line up, according to Sparavigna.
The theory is strengthened by the fact that several of the dodecahedrons have been found at Roman military sites. Sparavigna tells Mental Floss that “the small little studs [on the outside allow for] a good grip of the object. So an expert soldier could use it in any condition,” while the many pairs of holes allowed them to quickly select between a variety of ranges. “The Roman army needed a rangefinder, and the dodecahedron can be used as a rangefinder,” she explains.
But many modern scholars disagree. Historian Tibor Grüll of the University of Pécs in Hungary, who reviewed the academic literature about the dodecahedrons in 2016, points out that no two Roman dodecahedrons are the same size, and none have any numerals or letters engraved on them—markings you might expect on a mathematical instrument. “In my opinion, the practical function of this object can be excluded because ... none of the items have any inscriptions or signs on [them],” Grüll tells Mental Floss.
He points to the distribution of the objects as an important clue. They have been found across a northwestern swath of the former Roman Empire from Hungary to northern England, but not in other Roman territories such as Italy, Spain, North Africa, or the Middle East. That lack works against the idea that the objects were military devices. "If it was a tool for ranging artillery," Grull says, "why does it not appear all over the empire in a military context?"
Perhaps the dodecahedrons were used for play, not war. Some scholars have suggested they may have been part of a child’s toy, like the French cup-and-ball game known as bilboquet, which dates from the Middle Ages. Their shape also invites comparisons to the dice used for gambling, a common pastime in the Roman era. But most Roman dice were six-sided, smaller, and carved from solid wood, stone, or ivory. Plus, the differently sized holes on each face of the dodecahedrons makes them useless as dice: One side is always heavier than the other, so they always fall the same way.
Many scholars have suggested that the items had a special cultural significance, and perhaps even a religious function, for the peoples in the formerly Gallic regions of northern Europe. The 1939 discovery of a well-preserved bronze dodecahedron in Krefeld, near Germany’s border with the Netherlands, lends credence to this idea. The object was found in the 4th-century CE grave of a wealthy woman, along with the remains of a bone staff. According to an essay from the Gallo-Roman Museum at Tongeren in Belgium, the dodecahedron was likely mounted on the staff like a kind of scepter head, and "probably ascribed with magical powers, bestowing religious power and prestige on its owner."
Or perhaps they had a different kind of cultural significance. Divination or fortune-telling was popular throughout the Roman empire, and the 12 sides of the dodecahedrons could suggest a link to the astrological zodiac. Others have suggested a link to Plato, who said that the dodecahedron was the shape “used for embroidering the constellations on the whole heaven.” (It's not quite clear exactly what Plato was talking about.)
Rüdiger Schwarz, an archaeologist at the Saalburg Roman Archaeological Park near Frankfurt in Germany—where Campbell first identified the curious object he'd found—explains that any discussion of the cultural significance of the objects is purely speculative. “We have no sources from antiquity which give an explanation of the function or the meaning of these objects,” Schwarz says. “Any of these theories may be true, but can neither be proved right or wrong.”
Schwarz points to another theory: The dodecahedrons may have been a type of “masterpiece” to show off a craftsman's metalworking abilities. This might be why they rarely show any signs of wear. “In this respect, the technical function of the dodecahedron is not the crucial point. It is the quality and accuracy of the work piece that is astonishing,” he tells Mental Floss. “One could imagine that a Roman bronze caster had to show his ability by manufacturing a dodecahedron in order to achieve a certain status.”
SOLDIERS IN THE BACKYARD
Of course, the internet loves an ancient mystery, and ideas about the purpose of the Roman dodecahedrons have flourished there. The work of Dutch researcher G.M.C. Wagemans, detailed at romandodecahedron.com, proposes that the objects were astronomical instruments used to calculate agriculturally important dates in the spring and fall by measuring the angle of sunlight through the different pairs of holes. Other internet researchers, perhaps less seriously, have used 3D-printed models of the Roman dodecahedrons for knitting experiments, and suggested that the true purpose of the objects was to create differently sized fingers for Roman woolen gloves.
Campbell has taken his artifact to several museums in London, but beyond confirming what it is, they could provide no further clues about its particular origin or purpose. "Many [is] the time I have handled it wondering as to its exact use," he says.
While Campbell has no clear idea what the Romans were doing with the dodecahedron—which he now keeps in a display cabinet in his house—he does propose how it might have come to be in his garden: by being left behind by soldiers traveling between London and the early Roman provincial capital of Camulodunum, now Colchester in Essex. Romford was at that time a river crossing and the probable site of a fortified posting station used by Roman troops for changing horses and resting in safety.
“Two thousand years ago, I believe this area was forested and the River Rom's flood plain was much wider than today,” Campbell says. “I often form a picture in my head of 100 or so Roman soldiers in full uniform bedding down in the area, now the bottom of my garden.”
Roman dodecahedrons are still being found today. Recent examples have been unearthed by metal-detectorists in the north of England, and by archaeologists excavating a late-Roman rubbish pit in the north of France [PDF]. It's likely more will be found in the future.
But unless someone also finds an instruction manual—and after more than 1500 years, that seems doubtful—the Roman dodecahedrons will continue to baffle, and fascinate, for many years to come.