Would never admit to having friends that dumb!

Isaac Asimov pointed out that if you're shortsighted enough, the earth is flat. Ha, ha.
It's only when you look at the total reality that the earth takes shape.

Essay -- The Relativity Of Wrong by Isaac Asimov. [hermiene.net]

From the essay before he even gets to the 'oblate spheroid' level of detail.

Eratosthenes noted that the Sun cast a shadow of different lengths at different latitudes (all the shadows would be the same length if the Earth's surface were flat). From the difference in shadow length, he calculated the size of the earthly sphere and it turned out to be 25,000 miles in circumference.

The curvature of such a sphere is about 0.000126 per mile, a quantity very close to 0 per mile as you can see, and one not easily measured by the techniques at the disposal of the ancients. The tiny difference between 0 and 0.000126 accounts for the fact that it took so long to pass from the flat Earth to the spherical Earth.