Water Level Showing Mountain and Horizon Dip Due to Curvature

[FatPhil]

What would cause this 'edge'?

The edge?

 

[Mick West]

The edge?

The question is more what causes the FE "edge" when you are standing on the beach and you see a horizon that looks like it's barely 10 miles away (because it is).

An actual edge >5,000 miles away isn't going to do that.

 

[JMartJr]

What would cause this 'edge'?

In that model, there is an actual edge.

It's not clear to me that this would be true. On a flat earth you'd be looking through an order of magnitude or two more atmosphere at the horizon. The line of sight would likely become optically thick and look like a white haze. I don't think you'd ever see a sharp horizon line.
I took this picture with a 300mm zoom lens last week of the Pacific Ocean just after sunset. I can see a sharp edge and even see the *tops* of clouds poking up over the horizon.

I guess whether you can see it for the atmospheric haze depends on how high you go ( to get above more atmosphere) and how far from the center you are. Depending on which flat Earth model you are dealing with, a dome may prevent you from getting above the atmosphere, unless there is not dome -- it's hard, in a single point, to deal with the very many different attributes of the world-as-modeled-by-different-flat-believers!

I'd accept that at lower elevations, and/or further from the edge, or trapped under a low enough dome, you'd get just haze instead of a visible horizon. You just get have often enough in the actual world! If you were high/close enough to see the "edge as horizon" though, it would not rise to eye level as you ascend. In neither model would that happen.

Which leaves me still confused as to why flat Earthers insist that it does, when it doesn't, and that that confirms their model, which it wouldn't even if it did happen.

 

[Mick West]

Which leaves me still confused as to why flat Earthers insist that it does, when it doesn't, and that that confirms their model

The simple answer there is that their model is very loosely defined, and even then not self-consistent.

 

[JMartJr]

The question is more what causes the FE "edge" when you are standing on the beach and you see a horizon that looks like it's barely 10 miles away (because it is).

An actual edge >5,000 miles away isn't going to do that.

Indeed. I am certainly not arguing that the horizon as observed in the real world is compatible with a flat Earth. I'm speaking very strictly to the "horizon always rises to eye level" claim as a proof for their hypothesis that flat Earthers often advance. It does not, and would not in their model -- either you'd see no defined horizon, or it would drop below eye level if you went high enough or were close enough to see the edge.

 

[Rory]

I'd accept that at lower elevations, and/or further from the edge, or trapped under a low enough dome, you'd get just haze instead of a visible horizon. [But] If you were high/close enough to see the "edge as horizon" though, it would not rise to eye level as you ascend.

That's true - but would it even look like a horizon if it was at 'the edge'? Probably we'd notice there was something weird going on if we were there.

Really, it's an excellently simple flat earth disproof: there couldn't be any horizons on a flat earth unless you were close to the edge - and if you were close enough to see the edge you'd be close enough to see something so mindblowingly cool it wouldn't even be a question.

 

[AmberRobot]

The question is more what causes the FE "edge" when you are standing on the beach and you see a horizon that looks like it's barely 10 miles away (because it is).

An actual edge >5,000 miles away isn't going to do that.

According to Wikipedia, the Rayleigh scattering cross-section at 532nm is 5.1e-31 m^2. So at the red end of the visible spectrum, say at 700nm , it will be down to about 1.7e-31 m^2 due to the lambda^-4 dependence. The same Wikipedia article states the number density of molecules at atmospheric pressure is about 2e25 per cubic meter. So, for say 1000 km line of sight the optical depth would be about 3.4. At 532nm the optical depth would be over 10! So there's no way you could see a defined edge even if you discounted aerosols and only considered Rayleigh scattering. The horizon would look like a cloud.

As for going up in elevation that would help once you were really high, but remember that flat earthers often beleive that the atmosphere uniformly fills the space under the dome so there'd actually be *more* atmosphere to look through! They believe that must be true because they believe that the atmosphere would be sucked out into space in the globe model because they don't believe in gravity.

 

[FatPhil]

Really, it's an excellently simple flat earth disproof: there couldn't be any horizons on a flat earth unless you were close to the edge - and if you were close enough to see the edge you'd be close enough to see something so mindblowingly cool it wouldn't even be a question.

I'd add the word "clear" to that: there couldn't be any clear horizons on a flat earth ...
As we've seen in @Mendel's wonderful photographic thread, our bent earth does provide some wonderfully clear horizons. (Hat tip @AmberRobot too.)

 

[MyMatesBrainwashed]

Indeed. I am certainly not arguing that the horizon as observed in the real world is compatible with a flat Earth. I'm speaking very strictly to the "horizon always rises to eye level" claim as a proof for their hypothesis that flat Earthers often advance. It does not, and would not in their model -- either you'd see no defined horizon, or it would drop below eye level if you went high enough or were close enough to see the edge.

It has nothing to do with proving their hypothesis. That's not how flat earth works.

Flat earth spends most of its time trying to disprove the globe. On a globe the horizon can't rise to eye level. Therefore saying the horizon rises to eye level means it can't be a globe.

Nevermind it suggests a model with an infinite plane. "We don't have a model!!!!"