"People knew the Earth was round 2500 years ago. They just forgot.
Because Earth-bound observers could only view a small section of the globe at a time, it wasn't possible to tell from direct observation whether the Earth was a flat disk or a sphere. The Greeks were the first to theorize that the Earth was round. Scholars like Pythagoras in 500 BC based their belief on observations about the way the altitudes of stars varied at different places on Earth and how ships appeared on the horizon. As a ship returned to port, first its mast tops, then the sails, and finally its hull gradually came into view. Aristotle, who lived 300 years before Christ, observed that the Earth cast a round shadow on the moon. When a light is shined on a sphere, it casts the same shadow. The Greeks calculated the general size and shape of the Earth. They also created the grid system of latitude and longitude, so that with just two coordinates one can locate any point on the Earth. Greek philosophers also concluded that the Earth could only be a sphere because that, in their opinion, was the "most perfect" shape.
Around 150 AD, Claudius Ptolemy, a Greek geographer, mathematician, and astronomer, compiled an encyclopedia of the ancient world from the archives of a legendary library in Alexandria, Egypt. His eight-volume Geography included extensive maps of the known world, all based on a curved globe.
Unfortunately, learning and intellect went out of fashion in Europe between 400 and 1200 AD. The storehouses of Greek knowledge were lost to Western society with the advent of the gloomy period known as the Dark Ages. Sea monsters and Vikings ruled the seas, and ships that ventured too far from shore were sure to fall off the edge of a flat Earth. Maps made in that time were based on religious beliefs or superstitions, not on observations, calculations, or scientific inquiry. Rectangular maps of the Earth represented the "four corners of the Earth." Circular maps usually placed the birthplace of Christianity, the holy city of Jerusalem, at the center of the world.
After 1250, map making in Europe took a turn for the better. Land maps and nautical charts were produced for travelers using measurements and observation rather than mythology and literary sources.
In Europe, the Middle Ages progressed into the Age of Discovery. Meanwhile, the Arab world had preserved Ptolemy's Geography. Ptolemy's works were rediscovered by the Western world and translated into Latin. Ptolemy's map projections explaining how to represent a sphere on a flat piece of paper enabled cartographers and explorers to chart newly-discovered lands and seas. The invention of the printing press made it possible for more people to use, circulate, and refine maps.
Christopher Columbus' voyage in 1492 confirmed that the Earth was round. Magellan's crew proved the fact definitively by circling the globe on a three-year voyage from 1519-1522. Map making joined hand in hand with the Age of Discovery."
-- Some website that I can't post because Jiskha is being retarded.
Google query "discover round earth" and similar terms seem promising as well.
Jiskha is SO NOT retarded!!!! They help A LOT!!!!!!!
Way to blow my words out of proportion, there. That I can't post links to resources is what's retarded, not Jiskha as a whole, else I wouldn't be here, would I?
So, Jack, basically people thought the world was round, but in the Dark Ages they "forgot"?
Most people didn't even think about whether the world was round or flat. They lived their lives within a few miles of where they were born.
Since ancient times, a few educated people believed the world was round. The Vikings crossed the Atlantic Ocean from what is now Denmark to what is now southeastern Canada and founded a colony here.
Check this site to see what Columbus believed.
It's not saying the entire world knew that the earth was spherical and was suddenly struck by mass amnesia. This:
"The storehouses of Greek knowledge were lost to Western society with the advent of the gloomy period known as the Dark Ages. Sea monsters and Vikings ruled the seas, and ships that ventured too far from shore were sure to fall off the edge of a flat Earth. Maps made in that time were based on religious beliefs or superstitions, not on observations, calculations, or scientific inquiry. Rectangular maps of the Earth represented the "four corners of the Earth." Circular maps usually placed the birthplace of Christianity, the holy city of Jerusalem, at the center of the world."
Is the key text concerned with that.
I know that's not what it's saying. That's why I put forgot in quotes.
But aren't you implying that during the Dark Ages people may have thought the world is flat?
The person who wrote that article seems to be implying that, yes. I don't have personal knowledge of this but it makes some sense. I'd see if other sources say the same, though.