Let there be a firmament
And God said, Let there be a firmament [an expanse] in the midst of the waters, and let it divide the waters from the waters.
And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so.
And God called the firmament Heaven. And the evening and the morning were the second day. 1:6-8
This expanse was to house the sun, moon and stars; its size is immense, beyond our comprehension, as are the numbers of the stars that inhabit this expanse. The Hebrew word used here, rāqîya, conveys expanse. There are several references in scripture to God stretching out the heavens. Some use the verb rāqa which is related to rāqîya, others use the word nātāh, stretch out, spread out, extend, incline, bend. [BDBG] These are but a few of these passages.
Which alone spreadeth [nātāh] out the heavens Job 9:8
I am the LORD that maketh all things; that stretcheth forth [nātāh] the heavens alone; that spreadeth abroad [rāqa] the earth by myself; Isa. 44:24
I have made the earth, and created man upon it: I, even my hands, have stretched out [nātāh] the heavens, and all their host have I commanded. Isa 45:12
Into this expanse God was going to fit the heavenly host. 1:14-17. This was an awesome act of creation which only God, who is the author of time, could achieve at speeds far faster than the speed of light. God tells us what He did, we humbly accept that Word.
Where was this water placed? There is an interesting reference in Psalm 148:3-4.
Praise ye him, sun and moon: praise him, all ye stars of light.
Praise him, ye heavens of heavens, and ye waters that be above the heavens.
This passage is in harmony of what we are told in Genesis ch1, that there are waters beyond the stars. So it does not seem to be referring to a “cloud canopy” which provided water for the Flood, because the Psalmist spoke long after the time of Noah. (this doesn’t rule out that God did place water somewhere in space for this purpose, but that would be way below the stars, so it would not have been the waters referred to here. Also v8 says He hath also stablished them for ever and ever: he hath made a decree which shall not pass.)
Interestingly too at the end of Day second, there is no saying that it was good, as follows the other days. Was it that the “watery” works were not yet finished until the Day third with the separating of the water surrounding the earth into sea and land? This seems to be supported by the fact that the phase occurs twice concerning Day third. Once after the separation of land and sea and then again at the end of the Day.