If the truth shall kill them, let them die. Always learning & growing so never the same. Merely a humble student & no master.
If the firmament keeps water above/all around from coming in and they do all the NASA filming underwater, maybe it isn't to simulate space maybe it's because once you leave this dome/realm/firmament to go to another you travel through water to get there?
Maybe leave middle earth and go to outer earth
Antarctica and beyond
Outer earth maybe has another dome
VK said two domes.
