TIL about Sedevacantism, the belief that the current Pope is not Catholic and that there has not been a true Pope since John XXIII died in 1963, since all Popes after him accepted the Second Vatican Council which they call heretical

https://en.wikipedia.org/wiki/Sedevacantism

https://www.reddit.com/r/todayilearned/comments/1535zyk/til_about_sedevacantism_the_belief_that_the/