#The observed lack of curvature in overall space, known as the "flatness problem".<ref>If space were curved, one would never expect the universe as a whole to be almost precisely flat. Yet it is.</ref> | #The observed lack of curvature in overall space, known as the "flatness problem".<ref>If space were curved, one would never expect the universe as a whole to be almost precisely flat. Yet it is.</ref> |