Are the words "negative", "nego" and "niger", "nox" cognates?

Question

Are the Latin words "negative", "nego" and "niger", "nox" are cognates? In accordance to bible, word is a light and its absence is a dark.

Answer 1

A few things first:

• "Negative" comes from negō; the photography meaning came millennia later and isn't really relevant to the etymology
• Negō comes from the negater nē plus the old word for "to speak", which looked something like *agjō—so nē is what's relevant here

Now, for the three words in question:

• Nē goes all the way back to PIE without change; it's also the source of English negatives like "un-", "not", "no," and "never" (which accumulated other morphemes through Jespersen's Cycle)
• Nox comes from PIE *nokʷts, which might come from *n-gʷ- "naked"
• Niger's etymology is uncertain, but it might come from *nokʷts "night"

So, it's possible that nox and niger are related, but it's not completely accepted. It's pretty clear that nē isn't related within the timeframe that we can reconstruct; anything before that is pure speculation.

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P.S. In linguistics (and most other sciences), the Bible isn't generally considered a reliable source. While you may believe in it, many other people in the world do not, and it can't be backed up with evidence.