A Korean mathematician has won international recognition for solving a geometry puzzle that had resisted proof for nearly six decades.
US magazine Scientific American named the research by Baek Jin-eon among its top 10 mathematical breakthroughs of 2025, the mathematics community said on Sunday.
Baek, 31, is a research fellow at the June E Huh Center for Mathematical Challenges at the Korea Institute for Advanced Study.
The so-called moving sofa problem asks how large a rigid shape can be while still being able to pass around a right-angled corner in an L-shaped corridor of a constant width of 1 meter.
First posed in 1966 by Austrian-Canadian mathematician Leo Moser, the puzzle became widely known because it can be understood without advanced mathematics and has appeared in US textbooks.
Over decades, researchers proposed increasingly efficient shapes while narrowing the possible range of solutions, but were unable to prove where the upper limit lay.
In 1968, British mathematician John Hammersley introduced a shape with an area of about 2.2074 square meters.
In 1992, Rutgers University professor Joseph Gerver proposed a more complex curved figure with an area of roughly 2.2195 square meters, which became the leading candidate.
Although Gerver’s design emerged as the leading candidate, no proof had shown that a larger shape was impossible.
Baek’s work aimed to settle that question.
... continue reading