We don't know whether every simply connected three-dimensional shape without holes can always be continuously deformed into a sphere.
open
Global / Unspecified, Global
This question, closely related to the once-open Poincaré Conjecture, has been resolved in three dimensions but opens further mysteries in higher-dimensional analogues. Exploring these generalizations remains an active area of topology.
Citation ID: WS01242
Title: We don't know whether every simply connected three-dimensional shape without holes can always be continuously deformed into a sphere.
URL: https://worldsolve.org/index.php?api=problem&id=1242