A flat universe exists as far as we can see. You do not yet have the knowledge to explain or comprehend.
The current universe may perceived as flat.Proper collection of data will show the universe is limited and isolated in many dimensions.
The encompassed earth is not ready to calculate its surrounding energy. The species is not entirely ready. Hypersurface Theory for universe embedding will move to forefront.
Negative energy will sweep through the cosmos as a bubble as result of an adjustment.