Up until what date that men had thought the earth was flat

Question

and how did they theorize the edge of the world and whats outside? was there any more theories regarding the shape of the earth or universe before they came up with the idea of earth being flat. ?

Answer 1

In "recent" history, the idea that men used to think the Earth was flat came about at the end of the Middle Ages.

Very few people understood how things worked and it was inconceivable, for them, that anyone before them would have known any better.

But, they were wrong.

The classical Greek astronomers believed that the Earth was "round", with most thinking of a sphere, but still a good proportion going for a cylinder.

The cylinder gang had two sub-groups.  One believed that the universe revolved around a giant central fire.  Earth, as a cylinder, would keep one flat end turned towards the central fire, while we lived on the other flat end.

Light and heat from the central fire would come to us thanks to the sun, acting as a giant mirror.

A cylinder shape could explain the shape of the Earth's shadow on the Moon during Lunar eclipses.  But it could not explain why the declination of the overhead stars changed when the observer went to another latitude.  The Greeks often traveled to Egypt.

The other sub-group believed we lived on the curved side of the cylinder.  Geometrically, the curved side of a cylinder is a flat surface (meaning: the sum of the inner angles of a triangle is 180 degrees).  Which explained why we still observed the land as being flat.  It provided the explanation for the changing sky with changing latitude.

But it had other problems which were solved with a spherical shape.

The idea of a flat Earth became popular around the 15th and 16th century.  Was it from an over-analysis of Biblical texts?  Not sure.

A lot of our modern ideas about how ancient civilizations thought do come from such over-analysis, but that was a little later (after Magellan and Columbus).  For example, Ussher (from who we get the 6000 year old world) published his analysis in 1650, in between Galileo and Newton.

The fact that he did such an analysis is not surprising (it was the in thing to do at the time if you were into Biblical studies).  The fact that the figure is still used today is surprising, given that it was immediately rejected at the time (all the Church experts in this matter already knew that the world was over 7000 years old, they just did not know how much more).

The first formal indication (in a scientific work) that there used to be people thinking that the Earth might have been flat, came much later (18th and 19th century).  There is a famous woodcut, used as a cover on a book by Flammarion, showing a person arriving at the edge of a flat world and sticking his head through the celestial sphere to see outside.

The legend describes the scene as being of a Middle-Ages missionary finding the place where Earth and Heaven meet.

The more historians look into this, the more they are convinced that the idea (that men used to believe the Earth to be flat) is a 19th century invention, probably as an effort to present ourselves as far more intelligent than our ancestors.

Answer 2

We are not sure when people in general stopped thinking the earth was flat.  We do know that the Greeks in Alexandria had calculated the diameter of the earth (with terrific accuracy) as early as 300 BC.  We also know that all educated people (including Columbus) were aware of that fact when Columbus left Spain for India.

Answer 3

Actually, some still believe it. I think the Flat Earth Society still exists.

Answer 4

This site gives a pretty detailed discussion on the topic:

http://en.wikipedia.org/wiki/Flat_Earth

Answer 5

People knew that the earth was round 100,000 years ago, but 90,000 years later, most people forgot it, so they started thinking it was flat again. Then a few thousand years later people rediscovered the spherical earth again.