The discovery that the Earth is a spherical planet dates back to ancient times and cannot be attributed to a single person. Early Greek philosophers and mathematicians were among the first to propose and provide evidence for a spherical Earth.

• Aristotle (384–322 BC) was one of the first to recognize Earth as a sphere based on observations such as the circular shadow Earth casts on the Moon during lunar eclipses and the way ships disappear hull-first over the horizon

• Eratosthenes (276–194 BC) , a Greek mathematician and geographer, is credited with the first known accurate calculation of Earth's circumference. By measuring the angle of the Sun's rays at two locations in Egypt and applying geometry, he estimated Earth's size with remarkable precision

• The idea that Earth is round was well known in medieval Europe, contrary to the myth that people believed in a flat Earth until Christopher Columbus's voyages

• The first practical proof of Earth's roundness came from the Magellan-Elcano expedition (1519–1522) , which completed the first circumnavigation of the globe, conclusively demonstrating Earth's spherical shape

In summary, the concept of Earth as a sphere was discovered and developed gradually, with key contributions from ancient Greek thinkers like Aristotle and Eratosthenes, and later confirmed practically by explorers such as Magellan and Elcano