The canopy theory is a scientific explanation of Genesis 1:6, which refers to "the waters above the firmament" or "an expanse in the midst of the waters" that will "separate the waters from the waters." The word firmament, or raqiya in Hebrew, refers to the expanse above the earth, more commonly known as the sky. The Bible makes it clear that this word raqiya refers to everything above the earth—the place where the birds fly as well as the place where the planets spin (Genesis 1:20; Genesis 1:14–17). How did these waters get "above the sky" and for what purpose? What happened to the waters which were above the firmament? Is there any possible explanation for this phenomenon? These are the questions the canopy theory seeks to answer.
The canopy theory – What is it?
The canopy theory postulates that these "waters above the firmament" formed a canopy of water which protected the earth below and may have created a kind of greenhouse effect. The canopy theory usually suggests that it never rained until Noah's flood—that the canopy provided needed moisture for the earth. This would explain the lack of interest Noah's contemporaries displayed while Noah was building the ark. Perhaps he warned them of rains and floods, as God had promised, but since they had never heard of such a thing, or seen it with their own eyes, they were reluctant to believe. In any case, Noah believed God would do what He said (Genesis 7:4), and so Noah built the ark.
"In the six hundredth year of Noah's life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened" (Genesis 7:11). Advocates of the canopy theory have suggested that the rain falling on the earth to flood it, this opening of the "windows of the heavens," was the canopy falling to earth. There are a few scientific problems with that idea—the sheer amount of water that would be needed to flood the earth, if it all came from the canopy, would create an exothermic reaction (a great deal of heat) as it converted from a vapor to a liquid. An exothermic reaction of that magnitude would have literally cooked the planet.
This doesn't necessarily mean that there was no vapor canopy that collapsed into rain during the flood, only that it couldn't have provided the amount of rain called for in Genesis—five and a half weeks of continual rainfall—without also resulting in an exothermic reaction that would have cooked the earth. Some have postulated that a frozen canopy dissolving into rain (and producing an endothermic reaction) could have resulted in the Ice Age. However, if we remain faithful to the Genesis account, it is clear that Noah and his family lived on after the flood, and there is no mention of an Ice Age during their lifetime.
Since there is no canopy now, and the Bible does not explain where it went or what exactly it was, we can only speculate.
What is the firmament the Bible talks about?
Was the Noahic flood global?
Questions about Noah's ark: How long did it take Noah to build the ark? How long was Noah on the ark?
Faith vs. science. Is there a contradiction between faith in God and science?
Is creationism scientific?
Truth about Creation