Scientific American on Dec. 19, 2025 named the proof to the "moving sofa problem" devised by Baek Jin-eon, a research fellow at the June E Huh Center for Mathematical Challenges at the Korea Institute for Advanced Study in Seoul, as one of the American magazine's top 10 breakthroughs last year. (Korea Institute for Advanced Study)

By Lee Jihae

A domestic scholar's proof to a mathematical puzzle that had baffled experts worldwide over the past 60 years was named one of the 10 mathematical breakthroughs of 2025.

Scientific American on Dec. 19, 2025 placed on its year-end list the solution to the "moving sofa problem" by Baek Jin-eon, 31, a research fellow at the June E Huh Center for Mathematical Challenges at the Korea Institute for Advanced Study in Seoul.

The problem requires the finding of the shape of a sofa with the largest surface area that can fit through a narrow, right-angled corridor without getting stuck. First posed in 1966 by Canadian mathematician Leo Moser, the puzzle is easy to comprehend but remained unsolved for about six decades.

In 1992, Rutgers University professor Joseph Gerver proposed Gerver's sofa, measuring 2.21 square m wide with 18 curves, factoring in the order in which the couch touches the wall.

No one could prove that a sofa bigger than Gerver's could exist. Even Gerver himself only deduced that his sofa was the largest that could pass through a hallway but failed to prove this logically.

After seven years of research and drawing on knowledge from fields such as pure mathematics, geometry and computer programming, Baek proved Gerver's sofa was the optimal answer and announced his findings in late 2024 in Archive, a pre-release site for dissertations.

The mathematical world considers Baek's achievement as more than just a solution to the sofa's size. The geometric techniques used in the process of finding his proof can be applied in fields such as autonomous path planning for robots and precision engineering design in narrow spaces.

jihlee08@korea.kr