To me, it’s: That ancient people thought the Earth was flat.
We have records from around 430BC where Greek philosophers spoke of the Earth being a sphere. In 240BC the Greek astronomer Eratosthenes calculated the circumference of the Earth and was only about 2% out.
Speaking to all:
How did Eratosthenes get the circumference of the earth?
The length of shadows.
Now for those who believe such a science:
Let us pretend the earth is a ball.
In 24 hours, let us take the distance between the earth and the sun to be constant (not changing) (change negligible).
But in that same 24 hours, no shadow, short shadow, long shadow, very long shadow could be obtained.
So, constant distance, changing shadows.
Inference:
You cannot obtain the distance of the sun from shadows.
Conclusion:
If the distance of the sun cannot be obtained, Eratosthenes is finished!
Let us return to our senses.
You’re forgetting one crucial detail about Eratosthenes’ experiment: the measurements were taken at the same time, noon on the summer solstice, the time of minimum shadow length in both locations.