Mathematicians often deal in abstractions that are quite beyond the ken of non-mathematicians. For instance, in 1637, the Frenchman Pierre de Fermat conjectured that there is no whole-number solution for the equation An + Bn = Cn where N is greater than two. He famously wrote in the margin of a book that he had a proof for it, but he never wrote it down.

Most people think Fermat was mistaken, for the proof became a sort of holy grail of mathematicians. And it wasn’t until 1995 that the British professor Andrew Wiles published a proof of Fermat’s conjecture, using many 20th century techniques that were unavailable to Fermat. The proof runs 109 pages, and—trust me on this—if you don’t have a Ph.D. in math, you won’t understand a word of it.

Related: Math Forum audio/video and Connected Math.