[quote=whizzball1]
Technology couldn't overcome that radius.
[/quote]

Not modern technology.[quote=Legend]
But The System cleans out and disposed of uninhabited universes. This has been established.
[/quote]

If it was a while back, I don't remember that. But the point being there could be universes, similar to the one David is from, where only one planet has life. Also, the city was built to protect, and if any of those cultures were close to dying out, why wouldn't they agree to live in Waternaux in exchange for using their planet and surrounding areas for resources?