In before NOBODY CARES.
Theory 1: After Aelle and Neville transcended time and space, they decided to drop in on the Arcus Prima ten years or whatever in the future, just to say goodbye before finally becoming all...transcendy.
Theory 2: The "other world" the high priestess keeps referring to is actually Earth, which they found when they used the Emerald Rimaajon to open a wormhole. They came back years later for reasons unknown, possibly to tell the Simulacrum's citizens the good news or something, hence the happy dance.
They weren't actually there, you know. It was just for the viewer's benefit, a visual representation of them "dancing for all eternity" or something like that.
Theory 1 fits with the general feel of the show, but I personally think the second hypothesis has plenty of support too. The helical motors are clearly some form of FTL travel. Just that no one knows how to work them any more. The presence of a second Spring and Aelle's pocket music box going batshit may suggest that there's some kind of similar device buried under the ruins as well. The crater may be from the impact of some massive colony ship or something that crash-landed on the planet centuries ago, with the ruined city growing up around it.
Well I still think it's a good theory.
maybe the dykes in /u/ will care
Wow, late night /a/ is really pissed off.