On the second day God created a solid barrier to separate the original waters of chaos into two massive bodies of water. This barrier is called a "firmament" or "dome," depending on the translation.
    To understand what God accomplished, it helps to visualize biblical cosmology, that is, the Bible's picture of the universe (see Figure 1.2). Ancient people in the Middle East, including the Israelites, believed that the inhabited earth existed as an island of sorts, surrounded completely by water. Its existence was precarious at best, because the waters that surround the inhabited earth always threatened to break the dams and come flooding down on top of it. God actively kept the waters at bay.

Figure 1.2 Ancient Cosmology In the ancient understanding of the physical world, the inhabited earth was surrounded by water, at times imagined to be the mythic monster of watery chaos. The firmamant was a solid barrier that tamed these waters and allowed a realm of life to emerge and thrive.

    There were two great bodies of water. One above the sky, the source of rain and snow, and one below the sky, the source of oceans, lakes, rivers, and wells. While strange to us, this design made perfect sense to pre-scientific Mesopotamian minds. It is not difficult to see why. Beyond the sky on a clear day there is a vast blueness, in hue very close to that of the ocean. Looking over the horizon of the Persian Gulf or the Mediterranean Sea, water blended into sky, suggesting that they were made out of the same material. It is not surprising that they might have thought water lay beyond the sky in the heavens. And they may have asked, "Where do rain and snow come from?" Well, God opens the windows of heaven and releases them in measured amounts. This they could understand, though they knew nothing about the cycle of evaporation, condensation, and precipitation.

Creation of the Heavens, by Michelangelo (1475-1564) "And Elohim called the dome the heavens." 1512, Sistine Chapel ,Vatican, Rome -- CGFA