Many Biblical critics will argue that it could never rain enough to flood the Earth in 40 days. This is true, although, rain alone isn’t really the method described in the Bible anyway. Where did all the water come from?
In the six hundredth year of Noah’s life, in the second month, on the seventeenth day of the month, on the same day all the fountains of the great deep burst open, and the floodgates of the sky were opened. (Genesis 7:11)
Floodgates? The world as depicted in the Hebrew Scriptures (the Old Testament) is a flat Earth model (which is, of course, how it would appear to any pre-scientific society). It was a round disc supported by pillars. The sky above was believed to be hard (it is referred to as the “firmament”), and the stars were inserted into it like light bulbs screwed into a ceiling. There was a layer of water above that (giving the sky it’s blue color) and the domain of god, heaven, was above that.
So, the water from the flood came from both above and below.
Different translations of the Bible occasionally drop the word firmament, but the word is there in the original Hebrew and the King James Version does use it:
1In the beginning God created the heaven and the earth.
2And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.
…6And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters.
7And 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.
8And God called the firmament Heaven. And the evening and the morning were the second day.
9And God said, Let the waters under the heaven be gathered together unto one place, and let the dry land appear: and it was so.
10And God called the dry land Earth; and the gathering together of the waters called he Seas: and God saw that it was good.
14And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years:
15And let them be for lights in the firmament of the heaven to give light upon the earth: and it was so.
16And God made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.
17And God set them in the firmament of the heaven to give light upon the earth,
…20And God said, Let the waters bring forth abundantly the moving creature that hath life, and fowl that may fly above the earth in the open firmament of heaven. (Genesis 1:1-20 KJV)
Interestingly enough, the prophet Ezekiel has a vision of Yahweh sitting on this throne on the firmament:
22And the likeness of the firmament upon the heads of the living creature was as the colour of the terrible crystal, stretched forth over their heads above.
23And under the firmament were their wings straight, the one toward the other: every one had two, which covered on this side, and every one had two, which covered on that side, their bodies.
24And when they went, I heard the noise of their wings, like the noise of great waters, as the voice of the Almighty, the voice of speech, as the noise of an host: when they stood, they let down their wings.
25And there was a voice from the firmament that was over their heads, when they stood, and had let down their wings.
26And above the firmament that was over their heads was the likeness of a throne, as the appearance of a sapphire stone: and upon the likeness of the throne was the likeness as the appearance of a man above upon it.
27And I saw as the colour of amber, as the appearance of fire round about within it, from the appearance of his loins even upward, and from the appearance of his loins even downward, I saw as it were the appearance of fire, and it had brightness round about.
28As the appearance of the bow that is in the cloud in the day of rain, so was the appearance of the brightness round about. This was the appearance of the likeness of the glory of the LORD. And when I saw it, I fell upon my face, and I heard a voice of one that spake. (Ezekiel 1:22-28 KJV)