According to the sages, the earth is flat and is covered by the firmaments, like a domed cover over a platter. Thus, the heavens seal the earth on each side and above.
One of the sages, Rabbi Elazar, argued that G-d created Adam so tall that when he stood his feet were upon the ground and his head reached the skies. How did this sage know the height of Adam? He learned of Adam’s height from the implications of this verse:
“From the day that G-d created Adam on the earth and to the edges of heaven” (Deuteronomy 4:32) implies that Adam stood on the earth and his head reached the edge of heaven. A different sage, Rav Judah, estimated Adam’s height while prone — when Adam rested upon the earth his feet touched the dome of the heavens in the east and his head touched it on the west. How did this sage know the height of Adam? He learned of Adam’s height from the continuation of the above verse:
“From the day that G-d created Adam…from the edge of heaven to the edge of heaven.” This implies that his feet touched the eastern edge of heaven while his head touched the western edge.
The scholars asked: If so, with each sage estimating Adam’s height differently, the verses contradict each other. Answer: The height of the dome of the heavens above the earth and the distance between the two edges of the heavens where they touch the earth — from the eastern edge to the western — are the same. (The French sages of the 13th century, the ba’alei Tosaphot, asked: If so, when reclined with his feet touching one edge of the heavens and his head touching the other, how did he manage to get up and stand? Is this not like a man whose height is the same as the height and the width of his tent? Answer: He was in the Garden of Eden, where the distances were different.)
(Babylonian Talmud, Tractate Chagigah 12a)