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Inside a strange and enchanting jungle-themed gymnasium that had just turned 100 years old.

This story begins in the fourth dimension.

Or, more precisely, with a British mathematician who, in the late 1800s, was intrigued by the concept of the fourth dimension and how to teach it to selfless children.

Charles Hinton wore many hats. He wrote science fiction stories even before the genre existed—he called them "scientific romances." In Princeton, where he worked as a mathematics lecturer for a while, he invented a gunpowder-powered baseball pitching machine. He also practiced polygamy, which contradicted the norms and laws of his native England. When he was found guilty of bigamy in the 1880s, he was forced to move his young family to Japan, where he found work as a mathematics teacher.

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We'll leave all of that for a biographical film because, for the purposes of this story, Hinton was an unintentional inspiration for a jungle-themed gymnasium, the patent for which has just turned 100 years old.

It turns out that the story of the jungle-themed gym and its sibling, the monkey bars, is full of strange and delightful twists and subplots that take us from Japan to suburban Chicago and touch upon theories of child development and, yes, theoretical mathematics.

Imagined Dimensions in Bamboo Hinton was a mathematician who explored the concept of the fourth dimension and ways to represent it. His model of the tesseract as a way of representing the fourth dimension in geometric space has since inspired a whole range of science fiction works and films, from "A Wrinkle in Time" to "Interstellar."

However, it was while living in Japan that Hinton made a concerted effort to help his students grasp the concept of the fourth dimension.

"He said that, you know, the reason these students can't understand the fourth dimension is because they've never encountered the third dimension in childhood," says Luke Fannin, a primatologist and Ph.D. candidate at Dartmouth College, who became obsessed with uncovering the origin of the term "monkey bars" (more on that later) and ultimately became something of an expert on the Hinton family.

Hinton posited that since we spend most of our lives just walking in straight lines and not utilizing all three-dimensional space around us, it would be even harder for us to make a mental leap into the fourth dimension.

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His solution was to teach young children, including his own, to assimilate the third dimension. To achieve this, Hinton constructed a series of interlocking bamboo cubes for his children. He marked the bamboo in all three directions, Fannin says: "Where the joints would be, he placed X, Y, Z coordinates." He then attempted to turn these interlocking cubes into a game. "He would say, 'X2, Y4, Z3—go!' and all the kids would race to the correct coordinate," Fannin says.

If this doesn't sound like a fun game to you, you're not alone. And these bamboo cubes never really had much significance. But years later, Hinton's son, Sebastian, remembered how much fun it was to climb and swing on them.

"He says, 'This is what I remember. I don't remember any of the math, but I remember it being so much fun,'" Fannin says.

By that time, it was the early 1920s, and young Hinton had moved to Winnetka, Illinois, where he worked as a patent attorney. He dreamed of recreating the bamboo structure of his youth—minus the not-so-fun mathematical games—and one evening began describing his plans at a dinner party.

Winnetka at the time was a hotbed of progressive education. The village was enamored with the educational philosophy of John Dewey, which called for "educating the whole child." That meant not just teaching reading, writing, and arithmetic but also how to be healthy, active people.

So, as Hinton described his dream climbing structure to his dinner guests, including Winnetka's director of schools, Carlton Washburn, Fannin imagines Washburn's eyes widening before he said to Hinton, "We need to build this in the schools!"

Soon after that, Hinton began filing patents for his design, which he registered under a company he called JungleGym Inc. And the rest, as they say, is history.