A very interesting question that deserves a Biblical (and logical) answer.
Aptly, the questioner (psmith4405) argue that “[…] ‘...darkness was upon the face of the deep’ - this is a description of what the ‘heavens’ appeared ‘on the face of it’ (namely, as it would appear for an observer on the earth).” This is an illuminating detail. I have found a similar concept in the book ‘Life—How Did It Get Here? By Evolution or by Creation?’: “When examining the Genesis account, it is helpful to keep in mind that it approaches matters from the standpoint of people on earth. So it describes events as they would have been seen by human observers had they been present. This can be noted from its treatment of events on the fourth Genesis ‘day’. There the sun and moon are described as great luminaries in comparison to the stars. Yet many stars are far greater than our sun, and the moon is insignificant in comparison to them. But not to an earthly observer. So, as seen from the earth, the sun appears to be a ‘greater light that rules the day’ and the moon a ‘lesser light that dominates the night’.—Genesis 1:14-18.” (p. 25, § 2)
Returning to the core of the argument, I would present what Bible (and Logic) explains us about the very first stage of Creation.
The wording of Gen 1:1 compared to that of the subsequent verses makes clear that Gen 1:1 speaks about a time period previous the ‘6-days creation account’.
“A plural usage in [Gen] 1:1 would mean that the numerous bodies of heavens would have already been made and/or formed--which they weren’t on Day-One.”, is a correct conclusion of Bill Porter (bold is mine).
Also Dottard reaches – in the first instance – to a similar conclusion (bold is mine): “That is, Gen 1:2 is not part of the first day of creation activity. This means that we have Gen 1:1, 2 as an introduction and Gen 2:1-3 as a conclusion forming a simple envelope of the 6 days of creation. […] Further, there is no record (in Gen 1:1–2:3) of God creating planet Earth on any of the six days. Nor is there any record of creating the water covering the planet – this was apparently all done before the first day of creation week. […] Therefore, a simple reading of Gen 1:1–2:3 suggests that a formless, worthless, lifeless, watery planet already existed at (ie, before) the beginning of creation week. This suggests that God had previously created it.”
So, since Gen 1:1 is a description of a ‘Heavens and Earth’’s creation previous the ‘6-days creation account’, it is clear that the ‘heavens’ (שׁמים) described in Gen 1:8 (inside the Second ‘Day’ of Creation), must be a different ‘object’ as regards the ‘heavens’ in Gen 1:1 (שׁמים)! In fact, the ‘heavens’ (שׁמים) described in Gen 1:8 must be a local (in astronomical sense) expansion of space, all around the planet Earth.
But, what about the odd plural of this term (שׁמים)?
If we become acquainted with the Bible Hebrew texts we get to know that in a number of instances the Hebrew text implements a plural form (to the nouns) without a logical sense (beware, this is not a criticism about the inspiration-related holy spirit’s actions – that I firmly believe – but about the badly treatment of the texts of some – not ‘all’! – scribes of ancient times).
For some examples, we found in MT:
the ‘lives’ (חיים) of the core-tree of the Garden (Gen 1:9);
the ‘bloods’ (דמי) of Abel (Gen 4:10);
the ‘wisdoms’ (חכמות) described in Pro 1:20. In this latter instance, even an ultra-orthodox Hebrew scholar like Gesenius turned up his nose at this odd plural: “[…] wisdom (Pr I20, &c.) can hardly be a plural […] but is a singular […]) [Gesenius Hebrew Grammar, #124e]; see also Gen 3:8; 6:3; 7:4, 6, 12, 17, and many other instances.
So, we cannot invoke always the presence of a grammatical plural termination to conclude definitely something about the number of some nouns at issue.
Granted, in the vast majority of instances, the plural endings implemented on the nouns indicate exactly the grammatical number of these nouns (singular or plural). But, in a number of instances what seems a singular noun is – instead – a plural one, and the other way round.
Then, in these cases, we are compelled – often – to reckon on the Bible context and on Logic to settle these dilemmas.
We may ask – now - In this case, do we have enough elements (drawn by Bible context and Logic) to settle this dilemma? I think so.
First of all, regarding the expression ‘the heavens and the earth’ (Gen 1:1), we can say that though there is not present a merism, this expression - in all likelihood - is a semantic equivalent to the (relatively) modern noun ‘Universe’.
Here are some commentators statements, as well as Bible notes (all 'bolds' are mine):
Albert Barnes: “[This verse] asserts the creation of the heavens and the earth; that is, of the universe of mind and matter. […] This sentence [of] Gen 1:1 assumes the being of God, and asserts the beginning of things. Hence, it intimates that the existence of God is more immediately patent to the reason of man than the creation of the universe.” (Notes on the Bible, on Gen 1:1)
John Nelson Darby: “The fact is stated that God created all things, all man sees, all the material universe. ‘In the beginning God created the heavens and the earth.’” [Synopsis of the Books of the Bible, on Gen 1:1].
ESV Bible [Gen 1:1 (ft.)]: “Heavens and the earth […] The text indicates that God created everything in the universe. […] God […] is the Creator of all things that exist.”
Matthew Henry: “[…] the heaven and the earth, that is, the world, including the whole frame and furniture of the universe, the world and all things therein, Act 17:24.” [Commentary on the Whole Bible, on Gen 1:1].
Jamieson, Fausset & Brown: “the heaven and the earth – the universe.” [Commentary Critical and Explanatory on the Whole Bible, on Gen 1:1]
Keil&Delitzsch: “’In the beginning God created the heaven and the earth.’ […] This sentence, which stands at the head of the records of revelation, is not a mere heading, nor a summary of the history of the creation, but a declaration of the primeval act of God, by which the universe was called into being.” [Commentary on the Old Testament, on Gen 1:1].
NJB Bible [Gen 1:1 (ft.)]: “‘Heavens and earth’ are the ordered universe, the result of creation.”
A little detail: at the level of concept, we may mention that the Sumerian people, too – in his own language – called the Universe AN.KI, literally “heaven [plus] earth”.
Though the traditional translation of the Hebrew expression הארץ ואת השׁמים is “the heavens and the earth”, we may reassert that the comparison between the same noun (שׁמים) appearing in Gen 1:1, as well as in 1:8, forces us to conclude otherwise.
According the Bible account, only when – through the separation of the waters – was created (in a broad sense) the sufficient space to obtain an expanse, it did appear ‘the heaven’, not before (see also Job 9:8; Isa 40:22; 42:5; Zec 12:1).
I am convinced that the best treatment in this verse is to translate it at ‘level of expression’, instead of ‘at level of (single) terms’. This method clears up the dilemma of a שׁמים existing before the ‘6-days creation account’ (Gen 1:1) versus an existing שׁמים only inside the Creation’s Day 2 (Gen 1:8).
As Alberto Canen expresses this idea (bold is mine): “[…] by integrating ‘heavens and earth’ [the Bible writer] attempts to cover everything, all that exist [made of matter]. […] It is also possible that […] because in the Hebrew language there is no word that corresponds exactly to that idea [that is, the Greek kosmos], he [the Bible writer] uses this redundancy of ‘heavens and earth.’” [The Observer of Genesis, the Science Behind the Creation Story, p. 47 (of PDF file)]
Personally, I am convinced that the expression at issue (on Gen 1:1) well synthesizes the concept of ‘Universe’, because it did could be considered – from a very ancient man viewpoint - an ensemble of expansions of space (= heavens), as well as planets (= earths).
According the official paradigm, since the term translated ‘heaven/heavens’ seems to appear constantly (in MT) on the plural, we are forced to conclude that this noun had never a singular form. This conclusion is questionable. Why?
All the countable nouns – for Logic – must provide either for the singular, as well as the plural form.
That conclusion (the idea that שׁמים possesses only the plural form, and never the singular one) goes against an Hebrew particular syntactical structure, included in the Bible text.
Let we expand this last concept.
The Biblical Hebrew language, to express some superlative forms utilizes – sometimes – an alternative structure of terms.
עבדים עבד (‘servant of servants’) - in Gen 9:25 – namely, ‘the most humble of the servants’;
קדשׁים קדשׁ (‘Holy of Holies’) - in Exo 26:33 et al. - namely ‘the most holy of all’;
שׁירים(-ה) שׁיר (‘song of songs’) - in Son 1:1 - namely, ‘the superlative song’;
מלכים מלך (‘king of kings’). We found this expression not only in Hebrew (Eze 26:7), but also in Aramaic [מלכיא מלך - Ezr 7:12 e Dan 2:37], as well as in Greek [βασιλευς βασιλεων - Rev 17:14].
In all these instances (of this kind) each noun is mentioned twice, the first time on the singular form (‘servant’, ‘Holy’, ‘song’, ‘king’), and the second time on the plural form (‘servants’, ‘Holies’, ‘songs’, ‘kings’). This happens always. It cannot be otherwise, if we not want to lose the goal of this syntactical structure, namely, to highlight a single term (noun) over an ensemble of homologous nouns.
After this clarification, open the Bible – please – in 1 Kin 8:27.
Here we found the expression שׁמים(-ה) שׁמי, that includes the term we are discussing. Though the first noun (שׁמי) is – according the orthodox paradigm – a plural form, it is evident – by logic – that it must be considered a singular noun! In fact, many Bible translations set no store by this supposed plural form.
Moreover, as the Bible says, the term שׁמים is a kind of synonym of רקיע (‘expansion’), as we can see in Gen 1:8. Then, since רקיע is – indisputably - a singular-form term, also the matching term, namely שׁמים, it must be inflected on the singular form.
On the basis of all what is said we may conclude that also the term שׁמים had the corresponding form of singular of it, as – besides – all the concrete nouns have it. This conclusion was endorsed also by eminent scholars.
In fact, the Hebrew Dictionary of James Strong, commenting the term שׁמה, it states (bold is mine) that it is “a form being dual of an unused singular […].” Even the Gesenius-Kautzsch’s Hebrew Grammar admits that in primeval epochs existed singular (absolute) form of this term. According this text, this term at issue did could be שׁמי [§§88d, 96].
All this converging clues make me convinced that in Gen 1:1 the two term at issue (שׁמים and ארץ, according MT) were – originally - both on the plural form.
So, the Gen 1:1’s שׁמים would refer – as a real plural (numerical) form – to the countless ‘expansions/expanses’ of space that are scattered in all the huge universe. Differently, the term שׁמים (according MT; maybe, שׁמי in originally) in Gen 1:8 must be refer to the ‘local’ (in astronomical sense) expansion/expanse (רקיע) of space, which separates ‘the waters below (= seas)’ from ‘the waters above’ (clouds’ system)’.
Along the lines of these remarks, we may hypothesize that the (Gen 1:1) term ארץ originally was inflected on plural form, since the universe included - besides the space ‘expansions’ = ‘heavens’ - also countless heavenly bodies (‘earths’).
Gen 1:1 speaks about a time period previous the ‘6-days creation account’.
Since Gen 1:1 is a description of a creation (of ‘Heavens and Earth’) previous the ‘6-days creation account’, it is clear that the ‘heavens’ (שׁמים) described in Gen 1:8 (inside the Second ‘Day’ of Creation), must be a different ‘object’ of the ‘heavens’ in Gen 1:1 (שׁמים)!
Regarding the expression ‘the heavens and the earth’ (Gen 1:1), we can say that though there is not present a merism, that expression - in all likelihood - is semantic equivalent to the (relatively) modern noun ‘Universe’.
Also the term שׁמים had the corresponding form of singular of it, as – besides – all the concrete nouns have it.
In Gen 1:1 the two term at issue (שׁמים and ארץ) were – originally - both on the plural form.
I hope these information will be useful for all the believers in the Master of the Universe, the Lord יהוה, Father of our Lord Jesus Christ.