* Early Ideas: The idea of a spherical Earth was prevalent in ancient Greece, with philosophers like Pythagoras and Aristotle making arguments based on observations like the Earth's shadow during lunar eclipses, the appearance of ships disappearing hull first over the horizon, and the changing constellations as one travels north or south.
* Mathematical Proof: Eratosthenes is often credited with the first scientific measurement of the Earth's circumference in the 3rd century BC. He used geometric principles and observations of the sun's angle at different locations to calculate the size.
* Circumnavigation: The first circumnavigation of the Earth by Ferdinand Magellan in the early 16th century provided irrefutable proof of the Earth's spherical shape.
It's important to remember: The concept of a round Earth wasn't universally accepted until much later. Many cultures held different beliefs about the Earth's shape, and the idea of a spherical Earth was challenged and debated throughout history.
So, while Eratosthenes deserves credit for the first scientific measurement, the idea of a round Earth was developed and refined over centuries by many individuals and civilizations.
