January 5, 2026
Sofa, so good?
Six-decade math puzzle solved by Korean mathematician
Math whiz “solves the sofa” and the internet argues about hallways, proofs, and 3D next
TLDR: A Korean mathematician unveiled a 119-page proof claiming the “moving sofa” puzzle’s best shape is Gerver’s design, earning major recognition. Online, fans gush over his poetic process while skeptics ask for peer-review receipts and wonder if a 3D version will turn this hallway victory into a staircase saga.
A 31-year-old Korean mathematician, Baek Jin-eon, just dropped a 119-page proof claiming the legendary “moving sofa” puzzle is finally solved—and the internet immediately turned into a living room of opinions. Scientific American put it in their Top 10 math breakthroughs, and the thread’s “source police” showed up fast: “Source is Scientific-American,” declared one commenter, linking the big story and the HN thread. Others flexed receipts with the actual paper on arXiv and a friendly intro from mathematician Dan Romik’s site (link).
But the mood wasn’t just math nerds high-fiving. Romantics vs. Skeptics lit up the comments: one fan swooned over Baek’s poetic “dreaming and waking” research vibe—“beautiful!”—while pragmatists asked if this is truly done or just “claimed solved” until the Annals of Mathematics stamps it. The hottest tangent? 3D chaos: “Is the equivalent problem in 3D harder or easier?” Cue memes about moving IKEA couches, hallway “boss levels,” and arguments over whether pure logic beats computer-assisted estimates (Baek says he used logical reasoning, not just machines). Bottom line: Baek’s proof says the best shape was the 1992 Gerver design all along; the internet says, “Nice—now try it with stairs.”
Key Points
- •Baek Jin-eon published a 119-page proof arguing Joseph Gerver’s 1992 shape is the hard upper limit for the moving sofa problem.
- •Scientific American named Baek’s research among the top 10 mathematical breakthroughs of 2025.
- •Earlier candidates included John Hammersley’s 1968 shape (~2.2074 m²) and Gerver’s 1992 figure (~2.2195 m²).
- •Baek used logical reasoning rather than computer-assisted estimates to establish optimality.
- •The paper was posted on arXiv in late 2024 and is under review at Annals of Mathematics.