Long before astronauts captured the iconic images of Earth from space, the idea of our planet as a spherical entity was a subject of philosophical debate and curiosity. It was Pythagoras, the renowned 6th-century BCE Greek philosopher and mathematician, who played a pivotal role in shaping this concept.
Pythagoras, celebrated for his contributions to geometry with the Pythagorean theorem, extended his inquisitiveness to the heavens. His claim of Earth’s roundness was supported by a series of indirect observations. Sailors venturing southward from Greece noticed a gradual elevation of southern constellations in the sky, an inexplicable phenomenon if Earth were flat. Furthermore, during voyages along the African coast, beyond the equator, sailors observed the Sun’s position shift from south to north, contrary to their experiences in Greece.
A critical piece of evidence supporting a spherical Earth came from lunar eclipses. The Earth, positioned between the Sun and the Moon, cast a curved shadow on the lunar surface, clearly visible from Earth. This curvature was consistent with a spherical shape.
While it’s debated whether Pythagoras was the first to propose this theory or simply its most vocal proponent, his advocacy marked a significant milestone in human understanding of our world. This ancient wisdom, eventually confirmed by Eratosthenes’ experiments centuries later, laid the foundation for our modern perception of Earth, culminating in the breathtaking views shared by the Apollo 8 astronauts, who gave humanity its first glimpse of the “blue marble” from space.
Main image: An engraving of the sixth-century BCE Greek philosopher and mathematician Pythagoras, one of the early proponents of the idea that the Earth is a spherical object.