And God said, “Let there be a firmament in the midst of the waters, and let it separate the waters from the waters.” And God made the firmament and separated 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 there was evening and there was morning, a second day. (Genesis 1: 6-8) (Revised Standard Version-Catholic Edition).
The works of the six days of creation of Genesis chapter 1 and identifying those works can be followed with relative ease but the work of the second day and its interpretation appears historically to be troublesome or difficult as it appears even in the works of the Fathers of the Church who give various interpretations to the work of the second day of creation. Even today among biblical scholars, catholic or protestant, various interpretations are given. I hadn’t thought about this to much until about a month or so ago, following some thread here on this forum, the issue surfaced and made me think about it and do some research about it. I enlisted the help of St Thomas Aquinas and his exegesis of the work of the six days of creation found in his Summa Theologica, Part I.
Concerning the work of the second day of creation, St Thomas offers two explanations gathered from the Fathers of the Church. Firstly, some fathers explain the firmament as the starry heaven. Secondly, others explain the firmament as the cloudy region of the air in which water is condensed and falls to the earth to water it. According to the first explanation, waters have been placed by God above the starry heavens. This is the interpretation given even today by some modern biblical scholars and found in at least some catholic bibles such as the New American Bible. In fact, it seems to be the mainstream interpretation of modern catholic biblical scholars. The second explanation we could simply call the earth’s atmosphere in which the waters above the earth are collected in the clouds and falls to the earth in the form of rain, snow, or hail. In the Summa Theologica, St Thomas offers these two explanations of the firmament but he doesn’t seem to give a personal opinion of one over the other but seems to simply say that the scriptures lends itself to both.
At this point, I began to search the Holy Scriptures for clues as to the meaning of the making of the firmament on the second day which God calls heaven. What precisely did Moses mean by the firmament? It obviously had to do with the separation of the waters which covered the earth in the early stages of God forming the universe. The difficulty of the interpretation of the work of the second day lies in that God calls the firmament heaven and the firmament is mentioned in the works of days 4 and 5. At the same time, God seems to have already created the heavens in the beginning, “In the beginning God created the heavens and the earth” (Gen. 1:1). But, the heavens had no light as we can understand by the words “and darkness was upon the face of the deep” (Gen. 1:2. And then God created the light and separated the light from the darkness. And there was evening and morning, one day (Gen. 1:3-5). By this Aquinas understands that the ‘formlessness’ of the heavens, that is, being without light, is given formation by the creation of light. For light gives beauty to the heavens and the heavens are the source of light. We can also reason that by the creation of light which God called day, and He called the darkness night, and there was evening and morning, one day, that according to the understanding of the former peoples and ancients, the heavens were set in a diurnal motion. Now, if the heavens weren’t made until the second day, how could there be a first day of which the Scriptures speak of in Gen. 1:3-5 and where is the light and darkness or day and night?