Flat Earth is an archaic concept of Earth’s form as a flat plane or disk. Flat Earth cosmography was a common belief among many ancient cultures, including Greece up to the classical period (323 BC), the Bronze Age/Iron Age civilizations of Near East up to the Hellenistic period (331 BC), India through the Gupta period (early decades AD) and China into the 17th century.
Although the idea of a spherical earth was first suggested by Pythagoras, an ancient Greek philosopher (6th century BC), most pre-Socratics (6th-5th centuries BC) still used the flat Earth model. Plato, his former student, wrote in the 4th century BC about a spherical earth. By 330 BC, strong empirical evidence had been provided for this. The knowledge of the Earth’s shape and global distribution spread slowly beyond the Hellenistic world.
Modern flat Earth societies, and increasingly unaffiliated individuals who use social media, continue to espouse flat Earth conspiracy theories despite the fact that Earth is spherical.