Darkness & Nothing
For darkness to exist you need nothing to exist. Both are inseparable. If nothing doesn't exist there is always something and that something will always be visible to some other energy with the ability to recognize/interface with it.
What's invisible to human eyes is perfectly visible to other things.
Science has yet to treat theological documents as white papers. While ancient, primitive folks with little learning did not understand atoms or even air and believed that 'nothing' was emptiness and 'darkness' was present when they could not see as clearly by sunlight or flame - it doesn't mean they were right.
;-)