5th January

On this day in 1874, in a letter to Dedekind, Cantor asked if the points in a square can be put in one-to-one correspondence with those on a line.
Methinks that answering this question would be no easy job, despite the fact that the answer seems so clearly to be 'no' that proof appears almost unnecessary.
It would be three years before Cantor could prove the answer was "yes."