Not scientific fact

Early on this film states that it was scientific "fact" that the earth is flat until about 1500.

That's false. Just about everyone serious about anything that could be called science knew it was round in 1500. It is not very hard to tell, there have always been several ways to fairly easily figure this out readily available to humans, and serious thinkers about the issue in general had known about the roundness for many centuries before 1500.

I wonder why they say this myth as if it's a fact that everyone knows. I wonder how many people believe in this myth now. I wonder how the percentage of those who do compares to the percentage of people in 1500 who really believed the earth was flat. Certainly there were in 1500 plenty of uneducated and/or ignorant people running around who did believe it was flat.

I dunno. The idea that any serious thinker about the issue, in 1500, really believed the earth to be flat, just seems ridiculous to me. Much more so that all of science would think it. Certainly, if I was a person who nevertheless thought this myth was true, I would at least take a few minutes and just do a quick fact-check before claiming its truth in a film, especially one in which I was trying to educate people about something.