Throughout the long history of mankind.
The debate over the correctness of the round Earth theory and the flat Earth theory has always been a highly controversial topic.
Previously, when introducing Zhang Zai, the origin of the round Earth theory was mentioned:
It is generally believed that the round Earth theory officially appeared in the 6th century BC.
That is when the Ancient Greek mathematician Pythagoras first proposed the concept of the Earth.
Then by the 3rd century BC.
The scientist Eratosthenes, living in Alexandria, established the concept of the Earth using geometric methods and calculated the Earth's diameter.
However, what was not mentioned at the time is that Eratosthenes's method was actually quite clumsy:
He accidentally learned that on the summer solstice every year, the Sun's rays would directly hit the bottom of a deep well in Sai, which is in Aswan, Egypt.
At the same time.
