I am doing a little research on the firmament, that is; the concept of it.
It’s common knowledge – but still worth a second thought:
The word firmament comes from the Latin firmus, or “firm,” and this description of the sky as something solid reflects ancient ideas of the way the universe was constructed. The first stargazers imagined the sky as a sphere, and it wasn’t until the late 1500s that the idea of an infinite universe was seriously considered. Today the word firmament is mostly literary, used to poetically describe the visual curve of the sky.
Googling around I found this image:
The Flammarion engraving (1888) depicts a man, clothed in a long robe and carrying a staff, who kneels down and passes his head, shoulders, and right arm through a gap between the star-studded sky and the earth, discovering a marvellous realm of circling clouds, fires and suns beyond the heavens.
The caption that accompanies the engraving in Flammarion’s book reads:
A naïve missionary of the Middle Ages even tells us that, in one of his voyages in search of the terrestrial paradise, he reached the horizon where the earth and the heavens met, and that he discovered a certain point where they were not joined together, and where, by stooping his shoulders, he passed under the roof of the heavens…