I already did some previous researches and found a lot of explanations about the differences between "dark and "darkness", including answers to a question here in StackExchange, but I'm still in doubt about which one to use in some situations - and it's also hard to be sure when they are interchangeable or not. 

For instance, in the sentences below is the use of "dark" correct (or acceptable) or should I use "darkness" instead? Or maybe both words can be used without changing the meaning of the sentence.

> 
> Can you see that strange light blinking in the dark? It’s being up
>  there for more than an hour and none of us have any idea about what it
>  may be.
> 
> 
> And, even with all those clouds in the sky, we were still able to see
>  that tiny star shining far away in the dark.
> 
> 
>