Everyone knows that, in Greek mythology, Atlas is a Titan who was said to hold up the earth on his back… or is he?
In the original Greek myths, Atlas actually held up the sky, not the earth. In early times, the Greeks envisioned the sky as a gigantic bronze dome over the earth supported on all corners by mountains, except on one corner, where it was held up by Atlas. The reason Atlas was forced to hold up the sky was as punishment for having sided with the Titans in the Titanomachia, a ten-year war between the Titans and the Olympians, which resulted in the Olympians overthrowing the Titans and becoming the new rulers of the universe.
In later times, however, the Greeks figured out the world was round. (The philosopher Pythagoras of Samos is believed to have taught that the world was round as early as the 510s B.C. or thereabouts.) This posed a serious problem because, if the world was round, that meant that it would be impossible for the sky to be a solid, bronze dome over the earth. Greek sculptors and artists therefore began to portray Atlas holding a globe, except this globe was not the earth; instead, it was the celestial globe, a globe covered in the constellations. The celestial globe was intended to symbolically represent the sky.
Then, in later times, artists mistook the celestial globe for the terrestrial globe and began to portray Atlas holding the earth instead of the sky. Ever since then, people have been incorrectly describing Atlas as holding the earth, even though he originally was supposed to be holding the sky.
http://talesoftimesforgotten.com/2017/02/09/misunderstood-myths-part-five-atlas/