Chicago skyline proves curvature...

The vanishing point is the horizon. And the horizon on the flat earth is a ilusion. Our eyes have a CONIC VISION /\. When something go past the vanishing point, like the sun, it seems to "go down". See perspective diagrams to undertand.

So it's not the earth that curves, but our natural optical vision.

My guess ( since it's hard to do a experiment) is that the sun maintain his apparent size because of the atmosphere. If you look after images of sunsets, you see that the sun gets distorted close to the "horizon".

Here is a good video on that:



  

The trouble with these claims, flat earth and concave, is that I see no mathematics, and no well designed experiments... Just conjecture and opinion. And decent amount of condescending and bullying speech to the effect that those who believe the earth is round are stupid or blind. Those who support the flat or concave theories nearly to a person admit that they do not have the background in mathematics or physics to demonstrate or explain their claims, much less address the mountain of evidence to the contrary... And yet they pontificate as if they are experts, in general quoting other "research" that has been successfully debunked as either poorly done, misleading, or simply wrong. I find it oxymoronic that both theories are purported to be so "simple" as to be obvious to anyone who can read or look at a few pictures, but which nonetheless require a global conspiracy involving hundreds of thousands (if not millions) of scientists, for hundreds of years, across hundreds of nationalities and dozens of languages and cultures, all working in concert to fabricate one of the most startlingly elaborate hoaxes in history... Including fabricating millions of pages of scientific research and attendant mathematics, in addition to the photos claimed to be fake... All without a single credible witness ever coming forward to betray the conspiracy (in more than 500 years). The complexity and gargantuan nature of keeping such a conspiracy going in a way that is so nearly completely successful is both unprecedented in recorded history and inconceivable in human politics... There is no other example in history of something that big and that politically and technologically complicated ever working so well. And yet, those who suggest that concave or flat earth theories are so obvious because they are so "simple" in the following breath justify their beliefs by postulating the existence of the most complicated and mind numbingly intricate conspiracies ever conceived... Because presumably that is a simpler answer than that the earth is round.
One final question that's been nagging at me... If pictures, such as those from space, are so easy to fake in the modern age, why should you trust those which purport to support your theories any more than those which refute them?