Is the Earth a perfect sphere?
If you look around, the Earth looks flat. Even before the Middle Ages, people did think it was flat.
The flat Earth concept persisted till about 300 years ago. In fact, people used to think that if they sailed too far in one direction, they would fall off the edge of the Earth! Pythogoras was the first person to talk about the Earth being spherical. A practical demonstration of Earth being spherical was achieved by Ferdinand Magellan’s expedition’s circumnavigation.
image source: wikimedia commons
Well before Columbus sailed the ocean blue, Aristotle and other ancient Greek scholars proposed that Earth was round. This was based on a number of observations, such as the fact that departing ships not only appeared smaller as they sailed away but also seemed to sink into the horizon, as one might expect if sailing across a ball says geographer Bill Carstensen of Virginia Tech in Blacksburg.
It was Sir Isaac Newton who first claimed that the Earth is not spherical, but ‘oval’, he proposed that Earth was not perfectly round. Instead, he suggested it was an oblate spheroid—a sphere that is squashed at its poles and swollen at the equator. He was correct and, because of this bulge, the distance from Earth's center to sea level is roughly 21 kilometers (13 miles) greater at the equator than at the poles.