The Great Exodus? Not.
It is not true that "Lieutenant Felix Gaeta discovers that a nova occurred in the Ionian system which was seen around the same time as the Great Exodus." The Great Exodus was about 2,000 years ago, "around the time the 13 tribes first left Kobol." The Ionian nova was "seen 4,000 years ago, around about when the Temple might have been built," "which lines up with the exodus of the Thirteenth Tribe."
It's kind of besides the point, because you've obviously made a 2,000 year blunder, but I think this is how the scriptures make sense:
The 13th tribe left Kobol on a journey to Earth 4,000 years ago. (They, or somebody, soon resettles Kobol.)
The 13 tribes left Kobol for the Colonies 2,000 years ago.
The 13th tribe is all 12 tribes combined. And it is the rag-tag fleet presently; what happened 4,000 years ago is happening again now.
This is a bit speculative, and so should not go onto any pages, but I'm just trying to show you how it could make sense what they say on the show: the 13th tribe left Kobol 4,000 years ago (on a journey to Earth), and also the 13 tribes left Kobol 2,000 years ago (for the 12 Colonies.)
--MHall 10:54, 21 February 2007 (CST)