In the before time, how could it be said the Earth was flat when contary evidence was ever present on the very land they walked on and sailed on?
Of course, I refer to the distant horizon.
Would not Marco Polo have sailed (or walked) over the edge of the Earth?
By the time Marco Polo started his journeys, the idea of a spherical earth was winning. Here’s an interesting timeline (from Ethical Atheist, so could be seen to have a lean against Christianity).
Why believe in a flat earth? WAG: Because, perhaps, that was what folk saw in religious writings, and it reinforced the notion of man as being the reason for the existence of the rest of the universe.
I imagine that believing in a flat earth makes it easier to claim that some place is the center of the world, with the appropriate political or religious significance.
But it’s also true that if the world is round, it’s clear from the apparent local flatness that it must be very very big indeed, and it may be nearly as hard to believe in something that size as it is to believe in a small saucer a few hundred miles across on the back of an elephant.
Also, if the earth is round, how come we don’t fall off? Flatness makes more sense in a naive view of gravity.
It has been generally accepted since the time of the ancient Greeks that the world is round. There were some people who argued for a flat earth in ancient and medieval times, but that was definitely the minority opinion. In particular, Columbus did not have to prove to anyone that the earth was round. His only difference from most authorities at the time was that he had a different estimate of the size of the earth. He thought that the circumference was about 18,000 miles long. The standard authorities at the time thought that it was about 25,000 miles long, and they were correct, not Columbus.
I was taught in a History of Science college course that, civilizations dependent on the sea, such as the Greeks, knew about the earth being curved based on the argument that we see the top of the sail before we see the whole ship. However, the real fear was how far “down” one could sail.
On record, Magellan was the first who dared to try it. There was fear one could sail off the edge of the earth if one sailed too far south. Out of fear, his crew had a mutiny and killed him, IIRC. The trip was completed because the crew reached the point of no return, but Magellan didn’t live to see it, as so it was taught to me.
As for seeing a round moon in the sky, you could still argue the moon may be as flat as a pancake. Eclipses, also, give us just a 2-D perspective. At least, this could be how ancient man thought.
Hmmm, when was that famous experiment done in Alexandria, Egypt to measure the earth? I’ll look it up. If you recall watching the 1980’s PBS Series, “Cosmos”, Carl Sagan mentioned this…if he didn’t put you to sleep first! Man, that guy could take the excitement out of anything! He must have been a blast at parties! (We can thank Sagan for killing the general public’s interest in the heavens.) - Jinx
The famous experiment- That would be Eratosthenes. (Knowing that the sun at zenith could shine straight down a well at Syene and that Alexandria was due south of Syene at I forget exactly what distance… 5000 stadia, I think… he was able to compute the size of the Earth. )
As to eclipses, a lunar eclipse with a flat earth would project a line rather than an arc on the moon, wouldn’t it?
:;sigh:: :rolleyes:
It’s more surprising to me how early humans learned the earth was round than how late.
It wasn’t until the the 1800’s we knew germs caused desease but we knew pi, and how to calculate the sides of a right triangle WAY back.
A flat (disc-shaped) earth could cast any shaped shadow on the moon from a straight line to a circular curve, depending on the orientation of the earth in between the moon and the sun. The fact that the earth’s shadow is always circular proves that either the earth is a sphere, or that the circular, disc-shaped earth is always perpendicular to a line joining the moon and sun during eclipses.
-b
PS- I’ll have words with anyone who has bad things to say against Carl Sagan. 
(Although “Cosmos” did have bad clothes, bad hair, cheesy music, goofy sets, and those interminible sequences where Carl is piloting the space ship around.)
So if even the circumference of the earth was pretty well known (IIRC, Eratosthenes’ measurements were pretty close, and a replication of the experiment in Columbus’s time would have produced very good results), why did Columbus debate the common and correct wisdom that the earth has a circ of ~25,000 miles?
PS - second BryanMC. We have Carl Sagan and Cosmos to thank for much of our younger crop of astronomers, not to mention other kinds of scientists, and no other program since has communicated scientific thinking and knowledge nearly so successfully. And I even like the music and the visuals… and the clothes and hair are in style again.
A fine, informative contribution! At the risk of being redundant let me add that an account of Magellan’s journey can be found here, which doesn’t quite jibe with Jinx’s recollection.
Because the ships of the day could never carry enough supplies to sail the 10,000 miles from Spain to Japan, so he could never have gotten funding, or especially a crew, using the standard estimate. So he made up the data (or selectively used the little data that supported such a small distance) to get the smaller distance he wanted. For instance, he used the most exagerrated distances from Europe to China that he could find, and then decided that the Greeks had overestimated the size of the earth by about 25%. Basically, fraud – he used estimates to “remove” most of the western ocean in order to obtain funding. If the Americas had not been in the way for them to run into, they would’ve been screwed.