I post in these threads to make sure there are no misconceptions to newcomers.
The time that the flat Earth was the mainstream idea was before modern science existed, so your point is moot.
Sure, over 2500 years before "modern science existed".
But, in any case I don't recall mentioning modern science. Modern science has nothing to do with the case.
So when do you claim your so called modern science started?
Was it in the 13th century when
Iohannes de Sacrobosco wrote his treatise "De Sphaera" on the spheres, the earth and the celestial?
He wrote
THE EARTH A SPHERE. -- That the earth, too, is round is shown thus. The signs and stars do not rise and set the same for all men everywhere but rise and set sooner for those in the east than for those in the west; and of this there is no other cause than the bulge of the earth. Moreover, celestial phenomena evidence that they rise sooner for Orientals than for westerners. For one and the same eclipse of the moon which appears to us in the first hour of the night appears to Orientals about the third hour of the night, which proves that they had night and sunset before we did, of which setting the bulge of the earth is the cause.
And evidence "That the earth also has a bulge from north to south" and "That the water has a bulge and is approximately round".
Such "modern science"!
"De Sphaera" was regarded as one of the most definitive treatments of Ptolemaic cosmology.
Iohannes de Sacrobosco most assuredly believed the earth to be a Globe and with very distant sun, moon and stars.
Or did your modern science start in the 7 th century AD? When there were astronomers like
The Venerable Bede who categorically asserted that "
truly it is an orb placed in the centre of the universe".
Bede the Venerable
The monk Bede (c. 672–735) wrote in his influential treatise on computus, The Reckoning of Time, that the Earth was round. He explained the unequal length of daylight from "the roundness of the Earth, for not without reason is it called 'the orb of the world' on the pages of Holy Scripture and of ordinary literature. It is, in fact, set like a sphere in the middle of the whole universe." (De temporum ratione,). The large number of surviving manuscripts of The Reckoning of Time, copied to meet the Carolingian requirement that all priests should study the computus, indicates that many, if not most, priests were exposed to the idea of the sphericity of the Earth.
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Bede was lucid about earth's sphericity, writing "We call the earth a globe, not as if the shape of a sphere were expressed in the diversity of plains and mountains, but because, if all things are included in the outline, the earth's circumference will represent the figure of a perfect globe... For truly it is an orb placed in the centre of the universe; in its width it is like a circle, and not circular like a shield but rather like a ball, and it extends from its centre with perfect roundness on all sides."
From: Spherical Earth
I could go back to about 500 BC and find that the earth was even then thought to be a Globe.
Your flat earth is a comparatively modern invention, being quite unlike any early flat earth concepts, just read the history of the "armillary sphere" or the "spherical astrolabe" and see what some of the earliest ideas on the heavens were.
So your claim that you
"post in these threads to make sure there are no misconceptions to newcomers"
seems a little misguided.