The Toeplitz conjecture and perfect cuboid problem are among easy-to-understand geometry problems that remain unsolved. My other YouTube channels: The Science Fiction Rock Experience ( the music show I produce): null My science and music channel:: null Science World (with Emrah Polat): null My website: https://www.daviddarling.info/ My latest book is available here: https://oneworld-publications.com/work/the-biggest-number-in-the-world/