The Hardest Math Problem

Not about coronavirus just to cheer you up:

Puzzle. What math problem has taken the longest to be solved? It could be one thats solved now, or one thats still unsolved.

Lets start by looking at one candidate question. Can you square the circle with compass and straightedge? After this question became popular among mathematicians, it took at least 2295 years to answer it!

Its often hard to find when a classic math problem was first posed. As for squaring the circle, MacTutor traces it back to...