1.The Bible never said the firmament is visible or solid.
And God said: Let there be a firmament made amidst the waters: and let it divide the waters from the waters. - Genesis 1:6
A firmament: Strabus and Bede teach that there is an eternal heaven, because the firmament, which they take to mean the sidereal heaven, is said to have been made, not in the beginning, but on the second day: whereas the reason given by Basil is that otherwise God would seem to have made darkness His first work. Augustine says (Gen. ad lit. i, 9) that the heaven of the second day is the corporeal heaven. According to Damascene (De Fide Orth. ii) the firmament made on the second day is the starry heaven. Chrysostom understood that the heaven in 1:1 is the same heaven of the second day.
Divide the waters from the waters: Whether, then, we understand by the firmament the starry heaven, or the cloudy region of the air, it is true to say that it divides the waters from the waters, according as we take water to denote formless matter, or any kind of transparent body, as fittingly designated under the name of waters. For the starry heaven divides the lower transparent bodies from the higher, and the cloudy region divides that higher part of the air, where the rain and similar things are generated, from the lower part, which is connected with the water and included under that name.
- Thomas Aquinas
‘Day 1: In the beginning God created Heaven, and Earth. And the earth was void and empty, and darkness was upon the face of the deep; and the spirit of God moved over the waters. And God said: Be light made. And light was made. And God saw the light that it was good; and he divided the light from the darkness. And he called the light Day and the darkness Night; and there was evening and morning one day.
Day 2; And God said: Let there be a firmament made amidst the waters: and let it divide the waters from the waters. And God made a firmament, and divided the waters that were under the firmament, from those that were above the firmament, and it was so. And God called the firmament Heaven; and the evening and morning were the second day. God also said: Let the waters that are under the heaven [Earth] be gathered together into one place: and let the dry land appear. And it was so done. And God called the dry land, Earth; and the gathering together of the waters, he called Seas. And God saw that it was good.
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Let us use logic when reading the above creation by God. Day 1, God created the Earth and the spirit of God moved over the waters. We see then God obviously had created an Earth covered in waters. Water we know is essential for life and was used by God to cover the Earth once again at Noah's Flood. He then created a firmament, one that
divided the waters. The only logical meaning of this 'division' on day 2 is that God created a space between the divided waters. Now we know the clouds are waters so the only logical understanding of the firmament is that space between the clouds and the Earth, that space that contains the air totally necessary for life on Earth, that part of finite space God wanted us to know He created before the land-animals and mankind. We do not know of waters anywhere above the Earth other than clouds. Oh yes, the evolutionists keep looking for water outside in space in order to find life, and then intelligent life (aliens) outside the Earth. As it is heretical to believe in such life outside of Earth, those who place waters above the clouds are only contributing to this belief and search.
'And God called the firmament Heaven.' Heaven, as we all presume, is 'up there,' through the firmament into a finite space and on to heaven that exists outside of that space. Both Jesus and Mary, in their ascension and assumption up to heaven, went straight up from Earth to Heaven as depicted in images of both.