To understand Christian origins, it’s important to at least try to appreciate the cosmological worldviews of people living in the Middle East at the time of the New Testament. To that end, I am reproducing, with permission, a section from Mythicist David Fitzgerald‘s multi-volume Jesus: Mything in Action titled A Brief Tour of the Universe (Ancient Edition). This is from Chapter 17, Jesus in Hebrews, which is found in volume II, pages 196-7.
A map of the heavens drawn by Paul or the author of Hebrews would be a multilayered sphere, with the world at the very center (obviously). ¯11 In the first century, the “scientific” cosmology adopted by most religions was a geocentric spherical earth surrounded by concentric spheres of heavens, each one usualy associated with a planet (including the moon and the sun).
The first layer of heaven was the “firmament,” the foundation holding up all the rest. It consisted of all the air between the earth and the moon. Above that were several more layers of the heavens. ¯12 How many layers and what could be found in each depended on who was drawing the map. Being completely imaginary, there was naturally no end to scholarly debate on heavenly geography. ¯13
When Genesis was written, the universe was a modest three-level affair: the firmament was the basement of heaven, a solid dome over our flat round disk of an earth. God painstakingly attached the sun, moon, and all the stars (1:14-17) to the firmament, and above that was heaven itself. This is where God kept the “waters above;” by opening the windows of heaven, he poured them out upon the world during the great flood (Gen. 7:11, 8:2).
By Paul’s time, this quaint old-fashioned notion had been largely replaced by the modest ancient worldview that there were actually seven layers of heaven above the firmament (which extended from the earth to the moon): Mercury, Venus, the Sun, Mars, Jupiter, Saturn, (not always in that order), and above them all, the sphere of the stars. Astronomers debated whether the stars were distant suns; Jewish theologians favored the theory that the stars were a single layer of lights fastened to the top of heaven, and the earliest Christians readily accepted their view. ¯14
In this cosmology, the spheres of heaven were not vast expanses of cold, airless outer space vacuum. Each was filled with all manner of physical things: trees, gardens, rivers, palaces — everything you could find on earth you could find in heaven. In fact, everything on earth was merely the imperfect copy and shadow of the real things in the heavens, and as you ascended from heaven to higher heaven, the more real and perfect things became, the closer you drew to God.
In Jewish writings like the Testament of Abraham, Abraham finds all kinds of structures in heaven, such as gates, roads, halls and thrones as well as items like tables, linens, books with ink and quill, and so forth. The Revelation of Moses says Adam was buried in Paradise, up in the third heaven, complete with celestial linen and oils; in fact, he was buried in the same place where God took the clay to make him. ¯15 In the New Testament, Paul claims he knows a guy (probably himself, according to most scholars) who “was taken as far up as the third heaven,” into Paradise itself, where he heard “things that are not to be told, that no mortal is permitted to repeat” (2 Cor. 12:2-4).
¯11 We can’t tell if Paul was a flat earther, but (Richard) Carrier notes his education and fondness for stoic theology suggests not; only the most curmudgeony of later Christians rejected sphericity (private correspondence with the author).
¯12 Babinski, “The Cosmology of the Bible,” in The Christian Delusion, pp 109-47 (pp119-33 for the Biblical account)
¯13 For examples, see the rabbinical discussion in b. Talmud, Chagigah 12b & 13a
¯14 For example: Clement of Alexandria, Miscellanies 4.25 and 7.10 (57.5); Origen, On the First Principles 2.11.6-7; Irenaeus, Demonstration of the Apostolic Preaching 9. See James Tabor, Things Unutterable: Paul’s Ascent to Paradise in its Greco-Roman, Judaic, and Early Christian Contexts (Lanham, MD: University Press of America, 1986), pp. 63-68, 116-21.
¯15 In that book, Adam’s fall was literal: he was cast down from the third heaven to the earth below. His corpse had to be ferried back up by angels for burial. Revelation of Moses 21:6, 32-41 (esp. 32:4, 37-40); see also Tabor, Things Unutterable, p. 116