The Rubik’s Cube Turns 50

Early on the first Saturday in January, Tomas Rokicki and a few hundred other enthusiasts packed a large lecture hall in the Moscone Center in downtown San Francisco. A major math conference was in progress, and Rokicki, a retired programmer from Palo Alto, California, had helped organize a special two-day session of “serious recreational mathematics” to celebrate the 50th anniversary of the Rubik’s Cube. Erno Rubik, the Cube’s inventor, was the showstopper at 8 a.m., via videoconference from southern Spain.

Rubik, a Hungarian architect, designer, sculptor and retired professor, participated in a question and answer session with Rokicki and his co-organizers, Erik Demaine, a computer scientist at the Massachusetts Institute of Technology, and Robert Hearn, a retired computer scientist, of Portola Vallei , California.

Rokicki asked Rubik about the first time he solved the Cube: “Did you solve the corners first?”

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Today, new cubers learn on YouTube and watch tutorials at 1.5x speed. Rokicki instead recommends the old-fashioned strategy: set out on a lonely path and discover a solution method, even if it takes weeks or months. (It took computer scientist Donald Knuth less than 12 hours, starting at his dining room table in the evening and working into the morning.) Corners first is a common route, since once the corners are solved, the edges can be slid in. with relative ease. Rubik said that he did indeed do the turns first. Rubik, who is known to take a philosophical approach to cubology and life in general, added: “My method was understanding.”

‘Cubitus Magikia’

Rubik dates the Cube to the spring of 1974. While preparing for a course in descriptive geometry and tinkering with the five Platonic solids, he had become fascinated with the cube. But as he wrote in his 2020 memoir, “Cubed, The Puzzle of Us All,” for a long time “it never occurred to me that I was doing a puzzle.”

By the time of his 30th birthday, in July 1974, he had created the structure, realized its mysterious potential, and—after playing with it on and off for a few months—solved the Cube for the first time. He filed a patent application in January 1975, and in late 1977 the “Magic Cube” debuted in toy stores in Hungary. Travelers sampled it “in their luggage, alongside other Hungarian delicacies such as sausage and Tokaji wine,” he recalled.

One ardent exporter and ambassador was David Singmaster, a mathematician who wrote the book “Notes on Rubik’s ‘Magic Cube’.” In it, he outlined a notation for the faces — Up (U), Down (D), Right (R), Left (L), Front (V), Back (B) — that would help him orient the cube and refer to its pieces, positions and rotations. He also provided a step-by-step solution guide. And he reported a danger: Dame Kathleen Ollerenshaw, a British politician and amateur mathematician, had developed a case of “‘cubist thumb,’ a form of tendonitis that required a minor but delicate operation to relieve it.”

CubeLovers was one of the first Internet mailing lists — the inaugural message was sent in July 1980 by an MIT student: “I don’t know what we’re going to talk about, but a new mailing list can’t hurt (too much).” In March 1981, by which time the Cube had been renamed Rubik’s and was populating toy stores in the U.S., cognitive scientist Douglas Hofstadter diagnosed the craze as “cubitis magikia” — “a serious mental disorder involving itching of the fingertips, relieved only by prolonged contact with a multicolored cube,” he wrote in his column for Scientific American. “Symptoms often last for months,” he added. “Highly contagious.”

By November 1982, the mania had subsided — “Rubik’s Cube: A Craze Ends,” headlined The New York Times. But it was revived in the 1990s by the World Wide Web. In 2023, Spin Master, the toy company that now owns the brand, sold 7.4 million units worldwide, including both the classic Cube and its twisty puzzles. Ben Varadi, co-founder of Spin Master, noted that Rubik’s has “95% brand awareness” — virtually everyone has heard of it. According to Rubik’s lore, 1 in 7 people on earth have played with the Cube. “It gives me hope about the world,” Rubik told his audience in San Francisco. “It brings people together.”

Complexity from simplicity

After the session with Rubik, Rokicki gave a lecture on the mathematical aspects of the cube. He started with the fact that the cube breaks down into about 43 billion billion colorful combinations. “A pretty big number,” he said, possibly more than all the grains of sand in the world.

Part of the puzzle’s appeal is the complexity that comes from its simplicity. The cube consists of the 20 smaller “cubies” (eight corners and 12 edges centered between the corners) and six face-center pieces attached to the core. The core mechanism is anchored by a 3D cross, around which edge tabs and corner cubes interlock in a geometrically ingenious way, allowing the structure to rotate.

The cubes show 54 colorful facets, nine each of white, red, blue, orange, yellow and green. In the solved state, the six faces of the cube are configured so that all nine facets are the same color. Rotating the puzzle confuses the colors — in total there are exactly 43,252,003,274,489,856,000 possible positions in which the facets can be permuted.

All the while, the essential shape of the puzzle—the cube—remains unchanged. This feature is demonstrated by group theory, the mathematical study of symmetry: a so-called symmetry group of a geometric object is the set, or group, of transformations that can be applied to the object but that nevertheless preserve its structure. A square has eight symmetries: it can be rotated or reflected in four ways and it is still a square. A regular cube has 48 symmetries. The Rubik’s Cube has about 43 quintillion.

These symmetries are a “fantastic property,” Rokicki said, that “really gives the Cube its elegance.”

In a similar vein, the recreational math meeting included discussions about building an origami computer; the controlled art of juggling (as opposed to ‘joggling’, the uncontrollable pursuit of balls); and summary problems in knitting.

Barry Cipra, a mathematician and math writer, shared a wooden drawer puzzle he invented and called the Bricklayer’s Challenge. The setup: four rows of six brick-like blocks of varying lengths. The goal: arrange the bricks so that none of their vertical joints overlap adjacent horizontal rows.

As Cipra spoke, several spectators rushed to the stage (at his invitation) and got to work on finding one of the puzzle’s 2,184 solutions. Among the enthusiasts were Bram Cohen, a computer programmer (and the inventor of BitTorrent, a file-sharing protocol) who designs Rubik’s-like puzzles like the Maltese Gear Cube (in collaboration with Oskar van Deventer); and Rivka Lipkovitz, a high school senior and speedcuber (official personal best in competition, 14.71 seconds; personal at home, 10.75).

Cubic Encounters

There are many ways to solve the Cube. During his talk, Rokicki focused on a specific number: what is the minimum number of moves needed to solve even the most confused positions?

Rokicki set out in 1999 to calculate this quantity, known as God’s number. In 2010, he found the answer: 20. He had the help of many talented people, most notably Herbert Kociemba, a German hobby cuber and programmer known for his eponymous algorithm. The achievement also benefited from a lot of computing time donated by Google, and another algorithm that took advantage of the Cube’s symmetries, reducing the number of calculations required by a factor of 48, and in turn reducing the computing power required.

Rokicki’s current obsession is identifying all the positions of God’s numbers — they are “extremely rare, really hard to find,” he told the audience. As he spoke, three computers in his home were running at full speed — their combined 336 gigabytes digging out about 100,000 range-20 positions per day. So far, Rokicki has a database of about 100 million. “They are mathematical gems,” he said.

The Cube is also a good challenge for machine learning systems and robots.

And Maria Mannone, an Italian theoretical physicist and composer, invented the CubeHarmonic, a musical instrument developed with Japanese collaborators. “It’s a Rubik’s Cube where each facet has musical chords on it, and each facet has a note,” she explained in an email. “When we scramble the cube, we scramble musical chords.”

Parisian street artist Invader creates ‘Rubikcubist’ works, figurative canvases configured as a mosaic with hundreds of cubes. Invader’s version of ‘Les Demoiselles d’Avignon’, Picasso’s first Cubist painting, used 1,848 cubes to create a reproduction the same size as the original.

Lauren Rose, a mathematician at Bard College in New York, uses the Cube as a teaching tool in courses for both math majors (who delve into algebra) and non-STEM majors (who learn to solve the puzzle, explore patterns, configurations, and design and build mosaics). “There’s so much depth to this puzzle,” Rose said at the conference in San Francisco. She believes part of the reason the Cube has endured is because it’s “so accessible and fun.”

“It’s a good way to get people excited about learning math,” she added.

By now, all of the Platonic solids have been turned into squiggly puzzle variants. Moving on from the original, there’s the 4-by-4-by-4 Rubik’s Revenge, the 5-by-5-by-5 ​​Professor’s Cube, and on to the 7-by-7-by-7, the largest cube used in World Cube Association competitions. The 21-by-21-by-21 is the largest cube generally available on the mass market ($1,499.99). The 256-by-256-by-256 exists only in the virtual world, where it was solved by a team of six in 633,494 moves in a cumulative time of about 96 hours.

During the Q&A session, Rokicki asked Rubik about the hollow Void Cube, by Japanese inventor Katsuhiko Okamoto, who created dozens of variations of the original. Somehow, the Void is missing the central cubes and internal mechanics that hold Rubik’s iconic invention together. On this subject, Rubik became philosophical again. “Perfection is an idealistic encounter,” he said. He understood curiosity-driven explorations, adding something, taking something away. He preferred the classic combination of cubes and colors. “I also like the sound of the Cube, the movement,” he said.

Rubik later added that he was not so fond of puzzles that are just meant to be puzzles. He said, “I like the puzzling content of life and the universe as it is.”

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