First, I'm new here. I did scan the boards briefly to see if this has been covered. While I found related topics, I didn't see this particular point addressed.
I've debated enough FEers on YouTube to know that a common (and even lynchpin) "proof" posited by FE proponents is to the effect that, If the earth were a sphere then we should be able to see curvature on the horizon.
So my question is, What kind of curvature do FEers think we should be able to see on the horizon given a spherical earth? I've posed this question to many FEers, and no one has been able to answer it without introducing physical absurdities. Here is the extended version of the question I asked them. If any FEer here would like to attempt a cogent response:
When we look out at the horizon, we're not seeing the edge of the globe (yes, even flying at 100k ft). We're not even seeing a straight line that runs left to right. What we're seeing is simply part of a continuous horizontal circle called the "horizon" that extends around us for 360 degrees. It may look like we're seeing a straight line that runs left and right perpendicular to us when we're viewing it, say from a shoreline (where there are natural barriers that give it the appearance of a straight line). But that notion of the left-to-right straight line quickly vanishes once we take a row boat out to open sea -- or a plane to 100k ft -- where it becomes clear the horizon is just a flat, continuous 360-degree circle around us.
So I'd like an FEer to explain exactly what "curvature" you think we should be seeing at the horizon if a sphere framework is correct, because regardless of where you are geographically on a sphere, you will always be standing (or flying) at the top-center of that sphere. As such, all curvature for 360 degrees around you necessarily extends OUTWARD and AWAY from that top-center point. And since that curvature eventually enters the "hidden area" (the area beyond the vertical and downward curvature) there is no way to view anything beyond it.
Let's say you are standing on a flat plain with unobstructed views for 360 degrees. And lets assume for the sake of argument that we should be seeing curvature if the earth is a sphere:
Now you face east and see curvature at the horizon -- viz., the line of the horizon resembles an "arc" with the peak of that arc at the center of the horizon, with the north and south ends of that horizon line "dipping" downward ...
So you follow the "downhill" end that heads north to see just where that line "ends." To do so you must turn to your left to follow it (remember, the horizon is a 360 circle), and now that same horizon line is traveling west.
Now let's stop and think for a moment: If the earth is a sphere, should you expect to see a second curve that runs east and west as you face north? (here's a simple pictorial to help illustrate the attendant physical dilemma this creates):
https://drive.google.com/open?id=0B3HCADUuWwrMd1JrSm80UlFKM0E)
If so, we now have a problem. We now have TWO "arcs" -- one as we face east, and another as we face north. So now we should have a "valley" in the NE corner between those two hills, shouldn't we?
As you ponder what you should be seeing in the NE corner it occurs to you to turn in that direction and face NE. So now you're looking at the NE horizon with lines traveling NW and SE, and since (according to the FE lynchpin argument) you should be able to see curvature on the horizon no matter which direction you turn, you now see a third "arc" -- a NE-horizon arc, in addition to the earlier east-horizon arc and north-horizon arc.
In other words, what you logically "expected" to see was a valley but it turned out to be another arc. So now you're stuck with THREE arcs with TWO valleys separating them. But then as soon as you turn to one of those valleys you now have created a brand new horizon line and -- oops -- what you thought would be a valley is just another "arc." In fact, at every point where you think you should be seeing the "downhill" lines of an arc, it becomes part of the arc itself as soon as you turn in that direction, effectively cancelling out any possibility of "seeing" an arc-shaped curvature on the horizon.
It's impossible to see "arc" curvature on the horizon when you are standing on or even flying over top-dead center of a giant sphere because you're not actually seeing the edge of the sphere -- all you're seeing is a VERY small 360-degree horizontal circular area at the top-center of the sphere that we call the "horizon." It will simply appear to be a flat plain to you.
To illustrate that point, just imagine yourself standing atop a domed surface (say the Houston Astrodome). Now shrink yourself down to one-millionth your current size. Now scan the horizon around you in every direction. What do you think you would see?
Curvature?
Nope.
You would simply see a 360-degree view of a giant flat plain, period. It would appear to you that the surface is flat in all directions. You're simply too tiny to see the descending curvature of the dome even though you know it's there.
So, back to my original question: What exactly do you expect to see in terms of curvature at the horizon? And which horizon exactly? The one in the east? West? North? South? NE? NNE? NNNE? NEE? NEEE? Which one exactly, because the minute you identify a direction I'm just going to ask you to turn 1 degree to your left to create a new horizon, and whatever "arc" you've created with your horizon will quickly be canceled out by creating 359 rival arcs on 359 rival horizons. Claiming that because we don't see curvature on the horizon is frankly a silly argument because it assumes a physical absurdity.
Any takers?