Coventina's History Thread: Please stop with the Flat Earth Nonsense!

Even the ancient Greeks were able to get pretty close to estimating the circumference of the Earth.

Since ancient times, though, astronomers did believe that Earth remained a fixed point in the cosmos around which all other bodies - the Sun, the Moon, other planets, and the stars - revolved in an orderly, predictable fashion. This arrangement, called the Aristotelian system, satisfied most everyone because it could be proven by simple observation; a farmer, for instance, could watch the Sun rise in the east and set in the west.

It was not until 1514 that Polish astronomer Nicolaus Copernicus began popularizing the theory of helocentrism, which claims that Earth revolves around the Sun and not the other way around. The astronomer's theory was soundly criticized in his day (mostly by fellow scientists, and not so much by clergymen, as is often claimed). Subsequent studies showed Copernicus to be right, however, and the accepted wisdom of the previous 2000 years went out the window.

That is, until 1905, when Albert Einstein concluded that one could never really say whether the Sun revolved around Earth or vice versa; all you can say is that they move relative to each other. Beyond that, it's just a matter of perspective.