A Twitter spat between astrophysicist Neil deGrasse Tyson and rapper B.o.B over the flat Earth theory has turned into a full-blown rap battle.

B.o.B, whom you might know from his hits “Airplanes,” “Nothin’ On You” and “Strange Clouds,” kicked things off Monday when he started tweeting about how he believes the Earth is flat.

The rapper fired off more than 50 tweets, saying things like “I’m going up against the greatest liars in history … you’ve been tremendously deceived,” before Tyson took to Twitter to respond.

In a short series of tweets, Tyson explained why the Earth was round.

Tyson’s last tweet to B.o.B was, “Duude – to be clear: Being five centuries regressed in your reasoning doesn’t mean we all can’t still like your music.”

Naturally, B.o.B whipped up a song about the why the Earth is flat, called “Flatline,” that expanded on the theory, called out Tyson by name and also name-dropped David Irving, a renowned Holocaust denier.

Tuesday afternoon, Tyson dropped his own dis track, called “Flat To Fact,” written and rapped by his nephew, Stephen Tyson.

Alarmingly, B.O.B isn’t the first celebrity flat Earth truther.

Neil DeGrasse Tyson