The Earth Is Flat

... but SpaceTime is curved ...

It's not, but most of the time it's a very useful approximation.

At a dinner party with several academics, disciplines ranging from history to physics, I successfully maintained this assertion through all their attempts to find a contradiction. Given that for most people their direct experience is that the Earth is flat, and that the Sun goes around it, I sometimes wonder if it matters that they're "wrong".

The inability to find a contradiction merely proves that your world view contains no inconsistencies that the others could find. I would not be surprised if it truly was self consistent. That does not mean it is true. The earth not being flat was not proven mathematically; it was proven experimentally. Poles of the same length cast different length shadows at the same time of day on the same day of the year in sufficiently distant locations. People sailed around the world.

That misses the point entirely. In my model, poles of the same length cast different length shadows at the same time of day on the same day of the year in sufficiently distant locations. In my model, people sailed around the world. In my model, no experiment you can devise would show that the world is round. In my model, all experiments produce the same result as in your model of the round Earth, but in my model the Earth is flat. Why is your model "true" and my model "not true".

The people in question had at their fingertips (metaphorically) those experimental results such as poles and sailing round the world. They are insufficient to prove that the Earth is not flat. In my model the Earth *is* flat, and the model also predicts all these experimental results.

Where could we learn more about this model?

In your model of the (near) spherical Earth, take a line from the North Pole through the South Pole to infinity. Now apply an appropriate transformation to convert the universe into a half-R^3 with the Earth flat on the z=0 boundary plane. Every time you ask a question, perform the mapping to get the answer. This is provably self-consistent, and all experiments can be proven to give the same answers as in the usual model.

But now the Earth is "flat".

Before explorers made any recently accepted journey around the world, the current theories of the time made suggestion that the Earth is spherical. When explorers had maps to prove those theories, the theories became stated law. Observations from orbit and beyond support those original assumptions on the Earth being spherical. However, such evidence and assumptions don't also disprove any other possibilities; therefore, the spherical Earth is only the most popular assumption.

Mathematically, the Earth can take on any number of shapes or not be there at all. It all depends upon your point of view and how much trouble you're willing to go through to make use of such an assumption.

Actually, it's ellipsoid. The equator is slightly bulged out, mostly due to the earth's rotation.

Yeah, that's the more factual assumption, but what is the version most people know? Does it matter much to most people if the Earth is ellipsoid when all they really want is a round ball with a political map wrapped around it?

Most would be quite happy with a flat map cut off at the poles. Most Americans would probably be even happier if you cut off everything east of the Atlantic and west of the Pacific.

But then we wouldn't have the French to pick on. :) And GeorgeBush wouldn't have any countries to attack, unless he could make a case that Cuba had WMD's. (I can see it now: Bay of Pigs II, the sequel...) Hey, it worked for Kennedy.

And through one mechanism or another, they can logically justify such a view of the Earth. If a point of view supports that version, then it might as well be true, but what's easier for common people to assume? 'The Earth Is Round' is the thump from the elementary schools in the US and that's the version most people accept. Sure, the Earth is also ellipsoid any number of oids, but 'round' or 'spherical' is most likely what you'll be told in response to 'what shape is the Earth?'.

The point of claiming "the world is round" is to imply that the world is a 3-dimensional solid, and we live on its surface, as opposed to a 2-dimensional planar entity with an edge somewhere. NOT to claim that it is a perfect sphere, which it clearly isn't.

Relative to its size, the Earth is much closer to being spherical than any day-to-day object you are likely to find. And yet nobody complains when marbles are described in this way. It's because people are smart enough to know an idealization when they see one.

[deletion performed by script restored twice.]

Actually, IIRC the flat earth society still exists, and maintains the earth is flat. Where is the edge of the Earth? In Antarctica - according to this theory, the Earth is really shaped like a circle, with a center at the North Pole. The latitude lines form cocentric circles around the North Pole, with increasing radius as you go further south. At some point in Antarctica, one encounters the edge; the South Pole doesn't exist. Reported journeys to the South Pole are all fabrications, naturally, contrived by the GrandConspiracy to convince the foolish of the silly notion that the Earth is spherical. (Likewise for all the numerous photos supposedly taken from orbit - can you prove that they really were snapped from space?)

According to http://www.flat-earth.org/, they currently believe the Earth to be shaped like a pentagon. I'm not sure that site's official, however, as the FAQ seems a bit tongue-in-cheek. (Link broken; I get a 404 that ends with "Hail Eris". That's new.)

Of course, that doesn't explain why the lines of latitude grow shorter as you go south of the equator; the circle theory would predict that latitude lines continue to grow longer, in proportion to your distance from the North Pole. Nor does it explain the route that a direct flight from Buenos Aires to Pretoria would take... :)

: Actually your ruler (or other measuring device) gets longer as you go further "South", making it appear that the lines of latitude get shorter.

(Or maybe the earth is like a level in Pac-Man. It's flat, but if you exit on one side you are immediately transported to the other side...)

Actually you're all wrong - it's geomorphic.

Actually, we're all wrong. It's a fractal. You can't forget them mountains.

Yeah, a geomorphic fractal. Or is that a fractal geomorph?

PS: Recent studies have concluded that Kansas really is flatter than a pancake. Yeah, but how deep is Kansas as opposed to a pancake, hm?

So, if the Earth is flat, you would expect to find a country called FlatLand, yes?

The earth is NOT flat! Why, I can see at least three decent-sized hills just outside my window! Not to mention all them sticky-up trees and buildings and things. You call THAT flat??

And here I thought this page would be about The World Is Flat: A Brief History of the Twenty-First Century by Thomas Friedman (ISBN 0374292884 ).

There are still people who believe this kind of stuff. http://www.tfes.org/

this kind of stuff? it's the exact thing they believe

Also see: OccamsRazor