7 Thus 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.
8 And God called the firmament Heaven. So the evening and the morning were the second day.
Moses here in writing to Israel these words wants Israel to learn that the God who created the sky and the waters was the God they promised to serve. No one else. Therefore to worship the god of the skies and the god of the waters as worshiped by the pagans during their time is folly.
The earth originally had a water canopy that enveloped it. This water canopy might be one of the sources of water during Noah's time that rained on the earth and flooded it.
Henry Morris enumerates the effects of the presence of a water canopy
upon the earth. He suggests several effects of a vapor blanket.
i. It would serve as a global greenhouse, maintaining an essentially uniformly pleasant temperature all over the world.
ii. Without great temperature variations, there would be no significant winds, and the water-rain cycle could not form. There would be no rain as we know it today.
iii. There would be lush, tropical-like vegetation, all over the world, fed not by rain, but by a rich evaporation and condensation cycle, resulting in heavy dew or ground-fog.
iv. The vapor blanket would filter out ultraviolet radiation, cosmic rays, and other destructive energies bombarding the planet. These are known to be the cause of mutations, which decrease human longevity. Human and animal life spans would be greatly increased.
v. A vapor blanket would provide the necessary reservoir for a potential worldwide flood.
