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A 31-year-old Korean mathematician has just cracked one of geometry’s most stubborn puzzles, solving the moving sofa problem that has baffled the scientific community for nearly six decades. And he did it the old-fashioned way: with pure logic, no computers allowed.
The Problem That Sounds Simple But Isn’t
Imagine a rigid sofa trying to navigate a right-angle turn in an L-shaped hallway exactly one meter wide. What’s the largest shape that object could possibly have and still make it through without getting stuck? On the surface, it seems like something a teenager could solve with a sketch and some common sense. The reality is far messier.
This deceptively innocent question originated in 1966 when Austro-Canadian mathematician Leo Moser posed it to the world. It quickly found its way into American textbooks, captivating professors and students alike. For nearly sixty years, researchers have been chipping away at the answer, much like sculptors gradually coaxing a form out of marble.
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Six Decades of Incremental Progress
In 1968, British mathematician John Hammersley proposed a shape measuring approximately 2.2074 square meters. Two and a half decades later, Joseph Gerver from Rutgers University made a significant leap forward with a curved figure of 2.2195 square meters. Since then, no mathematician has found anything larger. But here’s the catch: nobody could prove that you couldn’t do better, either. The problem existed in a kind of conceptual weightlessness, with no clear theoretical framework to build upon.
Enter Baek Jin-eon.
A Researcher Obsessed With Missing Foundations
Baek first encountered this puzzle while working as a researcher at the National Institute for Mathematical Sciences, a role he took on during his mandatory military service. What grabbed him wasn’t just the question itself, but the absence of structure around it. Here was an enigma that seemed simple but remained unsolved, floating without solid foundations to stand on.
That missing framework became his obsession. For seven years, Baek pursued the problem relentlessly, first during his doctorate at the University of Michigan, then as a postdoctoral researcher at Yonsei University in South Korea. At 29 years old, he solved it.
His method was radically different from everything that came before. While his predecessors relied heavily on computer simulations to refine their estimates, Baek used only logical reasoning to establish that Gerver’s shape truly represented the insurmountable limit. No computer-assisted calculations. No brute numerical force. Just 119 pages of rigorously pure mathematical thought, each one packed with conceptual density.
From Quiet Persistence to Scientific Recognition
In late 2024, Baek published his results on arXiv, the preprint server where researchers share discoveries before formal peer review. The paper is now under evaluation at Annals of Mathematics, one of the field’s most prestigious journals. Scientific American recognized the breakthrough as one of the ten greatest mathematical advances of 2025.
To understand Baek’s dedication, you need to know where it comes from. He’s dreamed of mathematics since childhood. When he learned in third or fourth grade that he could study mathematics as a profession, it became his life’s ambition. Even when his family faced financial hardship, he never wavered. His passion isn’t performative; it’s cellular. As he puts it: “Even if I did something else, I don’t think I could abandon the beauty of mathematics.”
He describes the research process itself like an artist confessing to their craft. “You hold onto hope, then you crush it, and you move forward by gathering ideas from the ashes,” he explained in an interview shared by the Korean Institute of Advanced Study. “By nature, I’m rather a dreamer. For me, mathematical research is a repetition of dreams and awakenings.”
Now an Associate Researcher at the June E Huh Center for Mathematical Challenges at the Korean Institute of Advanced Study, Baek views his success not as a finish line but as a seed planted. “It takes time for a problem to gain its context,” he reflects soberly. With a touch of humor, Scientific American noted that solving the sofa problem the way Ross Geller would on Friends, complete with urgent “Pivot!” cries, required a 119-page proof.
Baek continues working on other optimization problems and challenges in combinatorial geometry. One sofa mystery fewer floating in the mathematical universe. Thousands more await.
