A little logic goes a long way
It doesn't take a lot of thinking power to put some pieces together and come to some basic conclusions. Unfortunately, there are many people out there who wish to defy all reasoning for the sake of being right.
Are you willing to consider that we're the only flat planet or flat anything in the whole known Universe? Every other body we've observed is either an oblate spheroid (ball) or a crab shaped galaxy. Ours just happens to be flat? Maybe a 4 year old can believe that, but as a reasonable adult, I require more evidence.
Claims require evidence. Extraordinary claims require extraordinary evidence. Period.
But why does the Earth look flat?
Some argue that the Earth looks flat when looking into the distance. That's one thing they got right. Seeing the Sun set doesn't mean it actually goes into the ocean. Oh, it goes somewhere, just not the ocean. Good thing our ancestors studied these phenomena a long time ago, which made us curious and made us do some actual research.
The reason the earth looks flat from your point of view (as seen by my crude drawing) is because there's a fall-off point in the distance. If you're on the ocean, or a large enough body of water, the fall-off point happens to be roughly the same distance from you. When you draw a line around your radius (distance from you) of the fall-off point, you're literally drawing a circle.
If the earth was truly flat, I'd be able to see cities in the distance, or at least other land masses.
90 Degrees of Separation
Yet, another crude drawing of mine. My math teacher in high school played this little game with us. He asked us, "Can you draw a triangle with more than 180 degrees"? We were baffled of course. He was much smarter than us; probably still is.
He said, "Imagine yourself at the north pole. Now, travel in a straight line to the equator. Turn 90 degrees right, and travel a quarter of the way around the equator in a straight line. Now take another 90 degree turn and travel until you get back to your point of origin."
Then he drew the sphere and three straight lines, connecting them by three 90 degree angles, making a triangle. BOOM!
If Flat Earthers really want to prove to us that the earth is flat, I'd love to see at least one of them try this "travel in a straight line" approach. Yes, you'd have to travel a LONG distance to prove it, but I'm sure they have the time. After all, they had time to look for photos of the arctic wall. Travel all you want, friends. After two turns, you'll end up in the same place. Oops.
No, I shouldn't have to do the travelling myself. You're the ones trying to prove me wrong. Safe travels.
Let's look at the night sky
It seems very clear that this would be impossible to observe if we were on a flat surface. I mean, the ONLY way this would be possible, is if we were truly on opposite sides of the disc... or, in our real world, the spheroid. There are videos like these ALL over YouTube. You can even find the night sky at the equator if you really want to see a different point of view. See below. Don't believe any of this? Visit Australia yourself sometime.
And there you have it. If anyone has any explanation to fit the Flat Earth model using the above evidence, please be polite, and explain. I'd love to discuss.
But What About the Lines of Convergence?
I absolutely love arguing this one. Apparently because the rays look like they're at an angle, the Sun must be closer than it really is. Unfortunately, some people didn't pay attention in geometry class.
It's like saying that this phone on the right has to be a trapezoid because of the way it's angled.
The Flat Earthers claim that the rays are converging to one point because of the way our eyes perceive the world. This couldn't be further from the truth. Each object that has parallel lines on it (such as the edges of this phone on the right) gives off the illusion that these lines meet somewhere in the distance. I dare you to try lines of convergence on a sphere. Automatic fail.
8 Inches per Mile Squared
One thing that Flat Earthers claim they understand is the curvature / drop off point of the Earth. They really do believe that the 8 inches per mile squared is how the Earth is shaped. No, I'm serious. They think the Earth has the shape of an infinite parabola. To calculate the Earth as a circle is out of their understanding of math.
So with that said, of course if you use a parabola, the drop off point comes much, much sooner. Unfortunately, since the Earth is really, really big, the curvature / drop of point isn't noticed at close distances.
So, to say that the point of visibility drops off at 8 inches per mile squared is either a lie, or a complete misunderstanding of the shape of a circle.
In fact, I was being generous when I drew the circle parabola figure on the right. Then, I did something more interesting. I actually did some real math, believe it or not. What I discovered was astonishing.
Not only are the Flat Earthers using an equation that doesn't match the circle model, but they also don't seem to understand how large the Earth actually is.
See images below of the calculated parabola of which they speak.
Fitting a Square Peg in a Round Hole
As you can see below, the 8 inches per mile squared idea fails miserably. Not only is the "calculated" drop of much, much greater on the parabola, which is what Flat Earthers claim it is, but the main understanding is that the rest of the world claims that the Earth's surface is fairly circular, and not an infinitely expanding parabola.
From the images below, based on the 8 inches per mile squared concept, travelling 1000 miles out should have us 1000 miles below the line of sight. On a circular Earth, we've only dropped 120 miles. Quite the gap. The further we travel out, the higher the discrepancy.
And of course, don't forget that based on this concept, we could technically travel out beyond the radius of the Earth and still be on the Earth. Sorry, it's just complete nonsense.
Considering that the US is severely behind in math, it's no wonder some people don't understand the difference between a circle and a parabola. The US ranks 31 out of 35 industrialized countries. That's almost last.
Want More Math?
Head over here to find out more math about it:
Or this page that shows you exactly what I'm talking about:
And then, this guy went all out to do much more in depth math:
But What About Planes?
Excellent point. While helicopters and planes travel about 2 miles above the surface of the Earth, it's still not enough height to see the curvature of the Earth. Check out the crudely drawn cone of sight from above.
The ISS is at a much, much higher altitude that can easily see the curvature of the Earth. Airplanes just don't fly high enough to notice. In fact, the ISS is at a height that's 12,000% greater than that of any airplane or jet known to us.
To see the curvature of the Earth and be able to detect it with the naked eye, you'd need to be way up there. 60K feet to be exact. Unfortunately, even the Concorde could only go up ~40K feet. Not enough to notice it with the naked eye, but maybe noticeable with very sensitive instruments? Like a really good ruler, maybe?
Pilots claim that you'd need to be at least 20 miles above the ground to see the curvature without any instruments. That's over 100K feet. That's a huge difference in height. 2 miles to 20 miles is ten times greater for those of you that can't follow.
It's not like comparing apples and oranges. It's like comparing coconuts and strawberries.
It's All About the Curves
This is the closest I can demonstrate the curvature of the Earth at high elevation until I can build a spaceship. Until then, download Google Earth and have fun. Make sure you close the photos pane and check out the elevation at the bottom right corner.
I would love to see any disputed video coming from a Flat Earther filmed at an altitude of 20 miles.