Of course, it’s not precisely one billion years in the future. The date isn’t 1,000,000,2013 AD. (No actual date, according to our system, is mentioned, because it’s irrelevant.) When you’re using numbers that big, you can round up or down a few million and not notice. More importantly, the people of the Ninth World don’t know the age of the planet, and they certainly don’t care how far separated they are from us. But we care. So let’s talk about a billion years for a moment–because it’s fun.
A billion years in the future puts the people of the Ninth World farther from us than we are from the dinosaurs, temporally speaking. By a lot of years. In this time frame, continental drift has brought the continents all back together again, and probably also seen them break apart again (in the Ninth World, this has happened and actually they’ve come back together again, but we don’t know if that’s natural or the product of some past technological workings). The sun’s luminosity should increase about 10 percent, drying up the oceans and making photosynthesis impossible. But in the Ninth World, there are oceans–actually there’s only one–and plants. So again, some kind of major engineering, even megascale engineering, has gone on here.
But here’s my favorite bit. Even by conservative estimates, assuming sub-light speeds, it would take a civilization about 50 million years to colonize the entire galaxy. In a billion years, this could have happened many times over. A billion years is enough time for a civilization to raise to a position of vast power (perhaps even being the seat of a galactic or even intergalactic empire), collapse entirely, and for the Earth to lie fallow for a long time to give rise to yet another civilization. And another. And another. Maybe some of these civilizations aren’t even human.