my challenge to the flat earthers

The average person, not having a college education in astronomy or geology, would likely find some flat-earth arguments "interesting". 

Exactly how much could you say about the coriolis-effect before researching it more than you already have? 

Exactly how much could you say, right now, without doing any further research that you ever did previously, about the inverse-square law?

See what I mean?

You would figure that the multitude of NASA space photos that show

a) earth where Brazil is seen in the center, and
b) earth where the north or south pole is seen in the center

.would convince flat earthers to change their mind, since the only way both such photos can be surrounded by a circular shaped earth is is for the earth to be circular all over (i.e., it is a sphere).  But no, they insist NASA photoshops all such images before daring to release them to the public.

You might wonder how some flat-earthers explain why it is that we can continuously fly from north to south and from east to west without ever encountering an ice-wall or going into outer space. 

What's east of New York?  Iraq.  What's east of Iraq?  China.  What's east of China?  Japan.  What's east of Japan?  Pacific Ocean, then Hawaii, California, and eventually New York again.  That is, you can travel in an easterly direction continuously and never once hit an "ice-wall" or perimeter you simply keep going until you arrive at the next place on the map, exactly as you would if the earth were a globe.

Nesbit says it's because when you travel too far into the ice-perimeter of the flat-earth, there is a time-warp that causes you to suddenly reappear at the opposite end of the earth.  See here.

Gee, you prop up your theory with a time-warp...then you chide everybody else for explaining the earth in ways that involve less mystery?  What's more absurd, space warps, or global shaped earth?

I haven't had the time to google every possible phrase that might provide a search hit showing somebody already thought of this, so here's my challenge to the flat earthers:

First, civilians are capable of launching a rocket high enough to see the shape of earth.  See here.
See lesser attempt of less financially funded persons such as a flat earther rocket launch here.

I see no reason why the Flat Earth Societies cannot pool their resources in the effort to conduct such a launch that would therefore be the "acid test". The rocket need not be very expensive, it is designed to do absolutely nothing but go up only as high as necessary for the entire circumference of earth to be seen..

Second, everybody except flat earthers agree that Brazil is at the "equator" of a spherical earth.

Third, get two such rockets.  Mount downward facing cameras on them, have them live-stream capable.

Fourth, set up the first rocket at the place us conspiracy theorists call the North Pole.  Set up the second rocket in some coastal city in Brazil, like Rio de Janeiro, so that when the rocket falls back to earth it will land safely in the sea instead of on land.

Fifth, stream the video to youtube, to make sure the raw unedited video is recorded by millions of people at the same time it is being streamed, as opposed to simply uploading the videos after they have been recorded and possibly subject to editing, which you know goddamn well will be what everybody says if you don't supply the video until later.  Think of how distrusting YOU are of NASA's space photos.

Sixth, launch the rockets at the same time, on a reasonably clear day.  The constant overcast skies of the north pole are irrelevant, if the rocket gets high enough, it's camera will show the entire earth, whether the portion directly below it is cloudy or not. 

Such a camera recording could also be obtained via high-altitude weather balloon, which .  See here and here.  Such weather ballooning has been the craze for some time and can be done for less than $1000.  See here.

If flat earth theory is true, only the Brazil-camera (i.e., the one furthest away from the ice-perimeter which flat earthers say the edge of the earth is composed of) will show earth to be a full circle.  The camera facing down on the North Pole rocket would, if flat-earth theory be true, not show a full circle.

Otherwise, if both videos show a  fully circular shape of earth, it would be perfectly reasonable to deduce that earth is shaped like a globe.  How would flat earthers explain a fully circular earth shape on the video recorded from the North Pole or what they believe is the "edge" of earth?  Is the edge of the earth fully circular when seen from above?  LOL.

With all the effort various flat earth societies put into debunking the spherical earth, this challenge would probably cost less than $25,000 in total costs to run, and is not asking too much.