Flat-earth believer B.o.B. battles Neil DeGrasse Tyson on Twitter

It all started Sunday when rapper-singer B.o.B. took to Twitter to preach the truth as he sees it. He wanted the world to know that the Earth is flat, despite centuries of evidence to the contrary.

Famed astrophysicist Neil deGrasse Tyson -- "one of the greatest liars in history," according to B.o.B. -- fought back with scientific facts and some personal digs of his own.

Finally, B.o.B. deployed a new tactic to make the case that the Earth is flat, via a new song. The track entitled "Flatline" includes quotes from Tyson and takes a direct hit at him: "Aye, Neil Tyson need to loosen up his vest/They'll probably write that man one hell of a check." (Warning: Some of the language is not suitable for kids.)

The rapper claims it's not a publicity stunt, though it's certainly succeeding in getting him in the public eye.

Amazingly, Tyson escalated the rap battle with a post of his own. "As an astrophysicist I don't rap, but I know people who do," he wrote. The track includes lines like: "The ignorance you're spitting helps keep people enslaved -- I mean mentally." Ouch.

Despite it all, Tyson suggested he's something of a B.o.B. fan -- of the music, anyway.