The other day I happened to look at the very first article in the Summa, and St. Thomas mentions an interesting thing. He just says it almost "by the way," as an example in a reply to an objection. He mentions that the earth is round. His reference makes it clear that educated people in the Middle Ages knew that.
I remember growing up hearing the story that Christopher Columbus was the first person to discover the earth was round. But St. Thomas knew it, and so did the ancient Greeks. Although scientists in our times have made astounding discoveries, the people in the Middle Ages knew more than we might suppose.