Here's an invalid math proof that was considered valid for 59 years.
In 1923, Henri Dulac published an accepted solution for Hilbert's Problem 16-II, for which he was awarded several prizes. In 1982, Ilyashenko and Ecalle found a gap in the proof that was only filled in 1992. pic.twitter.com/qevhkyeG5z
In 1939, George Dantzig, a graduate student at UC Berkeley, solved two open problems in statistical theory, which he had mistaken for homework after arriving late to a lecture by Jerzy Neyman. The two problems ended up being his entire PhD thesis. pic.twitter.com/5UzbaaQwne
