People have known the earth is a sphere since ancient times.
Flat earth mythology is of modern origin, mid-late 19th century, same time people came up with hollow earth (source of the “Middle Earth” mythology in the Lord of the Rings and such).
The “people used to believe the earth was flat” was a propaganda among late 19th century Science promoters that somehow stuck but modern historians do not hold that view of history.
But my rule holds: if it’s information in a Meme, it’s wrong.
This rule hasn’t let me down yet. smile emoticon