When did they realise that world was not flat?

Answer 1

The realization that the Earth is not flat began to emerge in ancient Greece, particularly around the 6th century BCE, with philosophers like Pythagoras suggesting a spherical shape. By the 4th century BCE, Aristotle provided observations supporting this idea, such as the Earth's circular shadow on the Moon during lunar eclipses. The concept became more widely accepted by the time of the Hellenistic period, around the 3rd century BCE, when Eratosthenes calculated the Earth's circumference. By the Middle Ages, the spherical Earth was a well-established idea among educated Europeans.