Ok real quick about “Earths”. This information mostly comes in handy when it comes to understanding the Train and the humans in Ileosa. The Train can only take humans and only from earth.
There are different versions of earth and they have their own little codes. Saul being from E-139, Eimantas being from E-404, Michael being from E-616 etc.
Earth versions are a play on the idea of alternate timelines, except in the Ileosa universe, not every action can create an alternate timeline. Earth versions are distinguished from one another through a key event that leads that version through it's own distinct development. This event can be small or large, it can bring about changes immediately or maybe in hundreds or thausands of years. Yet that key event happening alone is what creates the alternate earth version. There has also been a countable number of these key events, making the number of the alternate timelines not infinite and with potential to increase.
This means that some earth versions will look like the past or distant future of the modern earth you and I know, yet of course they will all be occuring at the same time. The Train that hops between these earth versions has no time travel involved.