> yes, I know that Eratosthenes measured the circumference in something like the 2nd century BCE.
That's not the point, the following quote from the article roywiggins linked you is:
“no educated person in the history of Western Civilization from the third century B.C. onward believed that the Earth was flat.”
> I mean, that's exactly what Columbus did a few hundred years ago. Should he have followed the 'scientific consensus'?
Besides being wrong, see above, that's not at all what I claim. If you think the scientific consensus is wrong, then prove it is wrong with evidence, write it up in a paper and submit it to a respected peer reviewed journal where it can be scrutinized. And don't try to circumvent review by presenting your work to the general public, who has neither the knowledge or the expertise to review your claims.
But until you've done that, your claims are just your opinion, and claiming they are 'proven' is bogus.