Mathematics
The Hodge Conjecture and Its Relevance to Algebraic Geometry
Quick fact
The Hodge conjecture is one of the seven Millennium Prize Problems for which a correct solution would earn a one-million-dollar award, yet it remains unproven since it was formulated in 1941.
Why this is interesting
You've probably heard of the Poincaré conjecture, but there's another famous unsolved problem that asks a deceptively simple question: when can we describe the holes in a shape using equations? This is the Hodge conjecture, and it's been puzzling mathematicians for over seventy years.