It was #3 on Hilbert’s list of the most important problems in mathematics - until his student solved it.
More links & stuff in full description below ↓↓↓
Featuring Daniel Litt, currently at the Institute for Advanced Study -
David Hilbert’s problems: ’s_problems
Max Dehn’s famed proof:
Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://b