system
A chat on 4chan
human
water being flat will not prove that the earth is flat or round. 
eratosthenes already calculated the earths circumference. 
please just let us as a species proceed and research so we can explore beyond the horizon atlas carries.
gpt
>eratosthenes already calculated the earths circumference.
Not actually accurate. Or at least, somewhat misleading. Eratosthenes already knew that the Earth was round, so his experiment assumed that and he was able to measure, fairly accurately, how big it is. But his experiment, standing alone by itself, would also work on a flat Earth with a nearby sun. In order to disprove the flat hypothesis, you need to do the same measurements he did, but at more points along the same line of longitude, and/or different lines of longitude. If you do that, you realize that any set of two different points on the same longitude give wildly different distance to the sun. (pic related). From multiple longitudes,latitudes, the bearings do not even intersect a common line, the sun is in all sorts of directions at the same time. On a flat Earth, bearings to the Sun make no sense at all.