The book of revelation is where the information comes from. You know, the Bible isn't so crazy. Not everything can be scientifically proven. In order for it to be scientifically proven it has to me measurable, tangible, and repeatable. History is none of those things. How do we believe that Socrates existed and was who we think he is? From the writings of Plato and several witnesses during the lifetime of Socrates stating all similar facts from all around the place. So we believe that Socrates was who they said he was from them.
I choose to believe the Bible because it is a reliable collection of historical documents written by eye-witnesses during the lifetime of other eye-witnesses recording supernatural events that took place in fofillment of specific prophecies and claim that their writings are divine rather than human in origin. And oh, by the way...i tried it. It changed my life.