Time for a Hebrew lesson:
השמים translated as The Heavens
The issue with this is that Hebrew is a concrete language and doesn't do well with abstract and "heaven" or "heavens" is an abstract translation. So how do the Hebrews see this word? First we're going to remove the ה from the word.
שמים which means desolate a possibility as it was all void but it gets better. ש and מים which shem (ש) as a prefix meaning as, leaving the rest of the word meaning waters. This makes perfect sense since the sky is filled with water and the sky above that is unbreathable like under the firmament - waters. Now that is a concrete word and a play on the word which Hebrew is filled to the brim with. The skies are like as waters. Same word. Praise the Lord! God is so cool!
Which is interesting since even in English we say sky or skies, water or waters, with subtile differences in meaning. God is specific and He shows that there are more than one heavens. And we know how perfect God is and accurate in His writing.