I did not know that the Ancient Greeks calculated the circumference of the Earth so early!

In China, the idea of a round Earth was not accepted till the 17th century.

An astronomer named Yu Xi postulated that the Earth is round in the 4th century, but not many believed him. Around the 11th century was when the trajectory of the sun and moon was calculated, but somehow people still believed in the "Round Heaven, Square Earth" thing (as in Earth is flat and square, enclosed by a round heaven.)

Even in the late 16th century when Jesuits brought maps and such, only certain scholars accepted it. Most thought it was foreign heresy. Then in the 17th century, Emperor Kangxi finally endorsed the idea. The concept was introduced as “Western knowledge that originated in China" in order to make it more palatable.

For thousands of years, Chinese astronomers maintained an unbroken, government-funded, detailed log of the sky. But the concept that China (more specifically the Emperor’s capital) is the center of the universe was so ingrained it felt like a betrayal to believe otherwise.