[Dr David Thork]

No, it isn't the edge of the earth, it is the edge of your perception.

If the first 50 miles is 2 inches vertical, and the next 50 miles is one inch vertical ... eventually 50 miles is a millimetre, then a nanometer to the point you can't tell how far you are seeing. It all merges into one and forms a curve around you with you at the centre.

[TomInAustin]

I'm not wrong. If the lens was a fisheye then the curve would be going toward from the center of the frame no matter what, but this doesn't happen.

You are wrong. This effect will be present in any camera lens currently in existence - a wide angle lens will exaggerate that effect, not introduce it. Also, how did you establish where the centre of the lens is in this footage?

Almost correct, any lens  (and excuse my terminology, its been years) that magnifies the image does the opposite, the lines curve inward.

http://www.idigitalphoto.com/dictionary/curvilinear_distortion

[ICanScienceThat]

Did they perhaps use one of these?  https://en.wikipedia.org/wiki/Rectilinear_lens

[Treep Ravisarras]

No, it isn't the edge of the earth, it is the edge of your perception.

If the first 50 miles is 2 inches vertical, and the next 50 miles is one inch vertical ... eventually 50 miles is a millimetre, then a nanometer to the point you can't tell how far you are seeing. It all merges into one and forms a curve around you with you at the centre.

So as said elsewhere, we simply leave the subject unknown. Could be a ball could be a flat disc, we just don't know as we cannot perceive the difference.

Is that what you mean?

But still, I think if it is flat disc as would not surprise me, we should be able to see the edge of it with a large telescope, no?

[Dr David Thork]

But still, I think if it is flat disc as would not surprise me, we should be able to see the edge of it with a large telescope, no?

No, but that is a discussion about meteorological visibility and not vanishing points.