What is the sun was smaller and closer than we think?
One could sew the same result in that instance.
One could sew the same result in that instance.
For practical purposes, we treat the sun as being an infinite distance away, and the error caused by it being ONLY 93,000,000 miles away is much smaller than Eratosthenes could measure :)
It's similar to drawing perspectives, you draw perspective lines to join at the distant horizon. You don't care how far to the distance horizon.
(Those ancient Greeks had amazing understanding of geometry. Much better than most of us.)
Apparently the ancient Greeks didn't have much, if anything, in the way of symbolic algebra or calculus - what we mostly think of as "maths".
Instead their normal tool for mathematical logic was geometry. An educated Greek would have used geometry much like we use algebra.
For most of us, given a non-maths problem (eg physics, chemistry, almost anything in real life...) the first thing we do is express it as an algebra problem, and solve that. The ancient Greeks used geometry in a similar way.