A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
dates back to ancient Greek philosophy
Ancient Greek philosophy arose in the 6th century BCE and continued through the Hellenistic period, at which point Ancient Greece was incorporated in the Roman Empire...
from around the 6th century BC, but remained a matter of philosophical speculation until the 3rd century BC when Hellenistic astronomy established the spherical shape of the earth
Shape of the Earth
Shape of the Earth may refer to:* Figure of the Earth, scientific measurement of the Earth's shape.* Flat Earth, a model of the Earth as a flat plane or disk.* Spherical Earth, a model of the earth as a sphere or oblate spheroid.-See:...
as a physical given. The Hellenistic paradigm was gradually adopted throughout the Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....
during Late Antiquity and the Middle Ages.
A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan
Ferdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....
and Juan Sebastian Elcano
Juan Sebastián Elcano
Juan Sebastián Elcano was a Basque Spanish explorer who completed the first circumnavigation of the world. As Ferdinand Magellan's second in command, Elcano took over after Magellan's death in the Philippines.-Early life:Elcano was born to Domingo Sebastián Elcano I and Catalina del Puerto...
's expedition's circumnavigation
Age of Discovery
The Age of Discovery, also known as the Age of Exploration and the Great Navigations , was a period in history starting in the early 15th century and continuing into the early 17th century during which Europeans engaged in intensive exploration of the world, establishing direct contacts with...
The concept of a spherical Earth displaced earlier beliefs in a flat Earth
The Flat Earth model is a belief that the Earth's shape is a plane or disk. Most ancient cultures have had conceptions of a flat Earth, including Greece until the classical period, the Bronze Age and Iron Age civilizations of the Near East until the Hellenistic period, India until the Gupta period ...
: In early Mesopotamian mythology, the world was portrayed as a flat disk floating in the ocean and surrounded by a spherical sky, and this forms the premise for early world maps like those of Anaximander
Anaximander was a pre-Socratic Greek philosopher who lived in Miletus, a city of Ionia; Milet in modern Turkey. He belonged to the Milesian school and learned the teachings of his master Thales...
and Hecataeus of Miletus.