User blog comment:Azecreth/Alternate universe help/@comment-4791767-20110214030123/@comment-26685181-20110214065926

Time travel, if it is used, is basically magic, and thus cannot play by the rules of science. It can't regimented and predictable, it can't be safe, and it can't be efficient. If it is, it's just too convenient and thus totally cliched. The crystal in First Strike is a good example of it.

Using your idea, I'd suggest the ships start out together, but end up landing at completely different points in time. The corvette arrives, say, 14.6 million years ago, and takes a nosedive into future Germany, lying undiscovered until WWII, when the Germans discover it, hoping to reverse-engineer wonder weapons. It's then captured by the Allies, and America's refusal to hand it over to the victorious Stalin being the real reason behind the Berlin Blockade, and jump-starting the modern technological revolution. The frigate arrives at the tailend of the 20th century, facing this changed Earth. The UESF (with a United Earth Space Corps?) is thus echnologically more advanced in important ways than the UNSC, such as DEWs, shields, FTL, etc, but socially stagnant and militarily inexperienced because with this technology, they never had the wars that the UNSC had to face, evening things up for the Progeny to gain a foothold.

On the other hand, with the Progeny, perhaps the lack of antagonism between the Elites and Prophets allows their technology to stagnate. It was the Prophets' exclusivity that helped them advance to far. Without being religious zealots, there's less coherency, and they're forced to fight wars against secessionists frequently, bringing them eventually into human space. Having read the UNSC frigate's records of the Covenant, the humans fire first and ask questions later, not knowing that events have turned out differently. The resulting war is one that humanity can actually fight the Progeny to a stalemate in.

See? If you take the predictability of time travel away, and tying it into real-life events, you can craft a more intricate backstory! Drop a pebble in water and you get rippled spreading outward, affecting each other and changing the flow of the whole river. The river is time, even though it isn't a river. It's an ocean.

Or, at least, that's what Michael Bay would have us believe.