So... Do we have any Flat Earthers here?

Where Fellowship and Camaraderie lives: that place where the CPS membership values fun and good fellowship as the cement of the community
User avatar
Rusty
Come and see the violence inherent in the system!
Come and see the violence inherent in the system!
Posts: 24938
Joined: Thu May 01, 2008 6:00 pm
Location: Beelzebub's Rare Tobacco Emporium

Re: So... Do we have any Flat Earthers here?

Post by Rusty » Tue Nov 14, 2017 9:29 pm

durangopipe wrote:
Tue Nov 14, 2017 8:47 pm
I'll let the comment stand. The earth is not flat, even locally. In this case the manifold is a heuristic, not a physical reality.

From Mathworld:

"Possibly what's confusing you is that the statement refers to the surface of the sphere, not the space the sphere is sitting in. If we ignore relativistic effects (and the fact that the Earth isn't quite a sphere), yes the sphere is in a Euclidean 3-dimensional space. In that space all the convenient Euclidean things apply. But the statement didn't refer to the sphere, or the space it's sitting in: it referred to the surface of the sphere. The surface of the sphere is a 2-dimensional space, not a 3-dimensional one, and points on it only need 2 coordinates (latitude and longitude, for example).

To help see the difference, consider a straight line between London and New York. In the 3-dimensional Euclidean space in which the Earth is embedded, that straight line goes through the Earth. But if we're only considering the surface of the Earth, that line doesn't exist. The straight line (shortest distance between the two points) on the surface lies along the great circle. Now consider drawing the lines from both New York and London to, say, Capetown, to make a triangle. Yes, if you draw the lines through the Earth you will get a nice Euclidean triangle with angles that add up to 180 degrees. But those lines don't exist in the space you are considering: you can only draw lines on the surface of the Earth. The angles of the triangle drawn on the surface of the Earth add up to more than 180 degrees, so the space must be non-Euclidean.

Edit: The bit after the "but" just seems to be saying that for most purposes you can treat a smallish bit of the Earth as if it were flat. You probably don't need to worry about the curvature of the Earth when looking at a street-map of your town."
I think we're agreeing at this point and esp. with that quote. Nobody here is saying that the planet isn't roughly spherical without any reference to scale. And there are certainly tools and techniques to detect the real shape of the planet. That has been true for a very long time. But none of us use spherical trigonometry to calculate distances, for example. We behave as if the earth is flat. The question is why is there a round/flat Earth problem and specifically why does it seem flat to us & our day to day behaviour assumes it is flat. And of course this was the observation of ancient people too. And I'm delighted to see the Wolfram article actually using our example to explain manifolds and esp to mention the flat/round Earth problem. This is not just a heuristic and this explanation actually played a roll in the development of manifolds.
Wolfram wrote:To illustrate this idea, consider the ancient belief that the Earth was flat as contrasted with the modern evidence that it is round. The discrepancy arises essentially from the fact that on the small scales that we see, the Earth does indeed look flat. In general, any object that is nearly "flat" on small scales is a manifold, and so manifolds constitute a generalization of objects we could live on in which we would encounter the round/flat Earth problem, as first codified by Poincaré.
I think the explanation is interesting and that is why I shared it (along with a bit of humour). And I hope that my original explanation has sufficient fidelity to the authoritative source so that it is useful.
Last edited by Rusty on Tue Nov 14, 2017 9:47 pm, edited 1 time in total.
A mood rises just to have.

Though it is not too sweet, the citreous marble design is refreshing womanfully, and a mood rises just to have.


~ Pen review (Onishi-seisakusho Fountain pen Acetate Lemon) on a Japanese site

Image

User avatar
hugodrax
All Around Nice Guy
All Around Nice Guy
Posts: 14545
Joined: Fri Jan 25, 2013 6:00 pm
Location: Pittsburgh, Pennsylvania
Contact:

Re: So... Do we have any Flat Earthers here?

Post by hugodrax » Tue Nov 14, 2017 9:40 pm

Goose55 wrote:
Tue Nov 14, 2017 9:15 pm
The earth is not flat, and it's also infinitesimally small compared to the now known universe. Lots of real estate out there. The Real Estate agent that told you "they don't make it any more" was lying.
They make more land on earth? Because, if they don't, he wasn't lying. You wouldn't survive anywhere else.
Etiam mihi opinio anserem perirent.

User avatar
Sir Moose
President Jar-Jar Binks fan club: "Meesa tink he da best!" - Perpetually in Trouble
President Jar-Jar Binks fan club: "Meesa tink he da best!" - Perpetually in Trouble
Posts: 2460
Joined: Tue Mar 03, 2015 1:17 am
Location: NW Washington
Contact:

Re: So... Do we have any Flat Earthers here?

Post by Sir Moose » Tue Nov 14, 2017 11:35 pm

hugodrax wrote:
Tue Nov 14, 2017 9:40 pm
Goose55 wrote:
Tue Nov 14, 2017 9:15 pm
The earth is not flat, and it's also infinitesimally small compared to the now known universe. Lots of real estate out there. The Real Estate agent that told you "they don't make it any more" was lying.
They make more land on earth? Because, if they don't, he wasn't lying. You wouldn't survive anywhere else.
It can certainly be argued that they're making more land.

New Island Appears Off U.S. Coast

Amazing pictures reveal new island in Pacific

Earthquake Births New Island off Pakistan
In theory, theory and practice are the same. In practice, they are not.

User avatar
hugodrax
All Around Nice Guy
All Around Nice Guy
Posts: 14545
Joined: Fri Jan 25, 2013 6:00 pm
Location: Pittsburgh, Pennsylvania
Contact:

Re: So... Do we have any Flat Earthers here?

Post by hugodrax » Wed Nov 15, 2017 9:04 am

Sir Moose wrote:
Tue Nov 14, 2017 11:35 pm
hugodrax wrote:
Tue Nov 14, 2017 9:40 pm
Goose55 wrote:
Tue Nov 14, 2017 9:15 pm
The earth is not flat, and it's also infinitesimally small compared to the now known universe. Lots of real estate out there. The Real Estate agent that told you "they don't make it any more" was lying.
They make more land on earth? Because, if they don't, he wasn't lying. You wouldn't survive anywhere else.
It can certainly be argued that they're making more land.

New Island Appears Off U.S. Coast

Amazing pictures reveal new island in Pacific

Earthquake Births New Island off Pakistan
Hmm, hadn't thought of that. Volcanic activity does it, too.
Etiam mihi opinio anserem perirent.

Post Reply