This verse has fascinated me for many years. Coming from a background of "King James Version only." I had always believed that the singular "heaven" of this verse was correct. I still do. After Bible College and Seminary, I was able to "use" the original languages (Hebrew and Greek), but I was confused because the word translated "heaven" is actually from the Hebrew shamayim which is plural. The KJV translates it in several ways, and my observation of these is that the translators were governed by using the context of the word. It makes sense for the word to be translated "heaven" in the first verse, IF one interprets the first verse as being part of the creative work accomplished on the first day. After all, the heaven or atmosphere (the space between the the waters called the firmament, the waters being the clouds and the oceans) was created on the second day. Just a side note here. There are three places called heaven in the Scriptures (2 Corinthians 12:2): the dwelling place of God, the universe beyond the earth, and the atmosphere where birds fly (created on day five).
If, on the other hand, the first verse is interpreted as an introductory statement of the creative work of God as a whole, then it could reasonably be translated "heavens." This interpretation also makes sense. That would mean that the creative work of the first day would be verses three through five. But, what do we do with verse two? Many respected theologians suggest that there is a gap between verse one and two. I won't go into a detailed explanation of what they believe occurred during this gap, but basically, they believe that God created a perfect, complete, inhabited world and that God destroyed it because it was contaminated by Satan being cast to the earth after his fall. This has been used to explain the fact that the earth was "without form and void" making it imperfect. It also is used to explain why there are dinosaur fossils which scientific experts claim are millions of years old.
My answer to this is that God, in verse one, created the materials He would use to mold and shape into the world as we know it. In verse one, the heaven is the space where God would put the sun, moon, and stars on day four. Notice that the Bibles says "the stars also." Regardless of differing languages, the fact that the stars are in addition to the sun, would challenge the "the known fact that the sun is a star. By now, I am sure that those reading this have written me off as a nut. All I ask is that the reader give serious thought to my understanding of the Word of God.. If, after sincerely evaluating my thoughts you come to the conclusion that I am wrong, so be it. I have been wrong many times; just ask my wife.
The reason I cannot accept the Gap Theory, is because the Bible clearly states that death was the result of Adam's sin. Romans 5:12 states, "Wherefore, as by one man sin entered into the world, and death by sin, and so death passed upon all men, for that all have sinned." If there was a previous creation and death occurred, then Romans is wrong; the Bible is never wrong! Nothing died prior to Adam's sin, including the dinosaurs. For a non-evolutionary explanation of creation, I recommend going to Answers In Genesis at www.AnswersInGenesis.org. There, you will find all the information you need to understand the earth is not millions of years old. It explains dinosaur and any other kind of fossils. By the way, if the earth was without form and void, it had to be without fossils. Void means empty. God bless you as you study His Word.