I honestly don't care whether anyone believes the Earth is flat or globular, but at least get the science right.
From the wiki:
Although the sun is at all times above the earth's surface, it appears in the morning to ascend from the north-east to the noonday position, and thence to descend and disappear, or set, in the north-west. This phenomenon arises from the operation of a simple and everywhere visible law of perspective. A flock of birds, when passing over a flat or marshy country, always appears to descend is it recedes; and if the flock is extensive, the first bird appears lower or nearer to the horizon than the last, although they are at the same actual altitude above the earth immediately beneath them. When a plane flies away from an observer, without increasing or decreasing its altitude, it appears to gradually approach the horizon. In a long row of lamps, the second, supposing the observer to stand at the beginning of the series, will appear lower than the first; the third lower than the second; and so on to the end of the row; the farthest away always appearing the lowest, although each one has the same altitude; and if such a straight line of lamps could be continued far enough, the lights would at length descend, apparently, to the horizon, or to a level with the eye of the observer.
This is entirely correct. 100%. So far so good.
This explains how the sun descends into the horizon as it recedes.
Just to be clear, the preceding does
not explain how the sun descends into the horizon. It describes how
any given point descends into the horizon, and the Sun is made of obviously a lot of points, but the distinction is critical because it purposely gets blurred later on to suggest perspective accounts for the image of the sun setting.
Once the lower part of the Sun meets the horizon line, however, it will intersect with the vanishing point and become lost to human perception
Yes! That is correct! But here's where that distinction is blurred. If this is all due to the Sun receding, then once the lower part of the Sun meets the horizon,
the upper part of the Sun must also meet the horizon. For an object to actually hit the infinite perspective point, it must be infinitely far away. Every point of that object will have converged at the perspective point, and it will be invisible. It's why objects get smaller as they get farther away. You can't have the bottom half of an object infinitely far away and the top half the same size as it was when it was overhead. Perspective doesn't work that way.
as the sun's increasingly shallow path creates a tangent beyond the resolution of the human eye. The vanishing point is created when the perspective lines are angled less than one minute of a degree. Hence, this effectively places the vanishing point a finite distance away from the observer.
Sure. Since the human eye has limits, we can't see something when it becomes extremely small.
But the size of an object doesn't have anything to do with where the vanishing point of perspective is. Let's say you have two geese flying next to each other, maybe 100 feet apart. As they fly away from you, not only are they getting apparently smaller, but they're getting apparently closer together because their straight lines of flight are following those converging lines of perspective. After say half a mile, just before you lose sight of them, you can see they aren't apparently touching. So in the next second, when you
have lost sight of them, did they suddenly zip together and appear to touch? Of course not because they're still following those lines of perspective. The size of an object has nothing to do with where the actual vanishing point of perspective is.
Usually it is taught in art schools that the vanishing point is an infinite distance away from the observer, as so:
However, since man cannot perceive infinity due to human limitations, the perspective lines are modified and placed a finite distance away from the observer as so:
Wait, who said humans can't perceive infinity? The last paragraph said humans can't perceive objects less than one minute of a degree, but whether we can perceive an object or not has nothing to do with where its perspective vanishing point is. That's not the same thing. It's a bit of a moot point because there's nothing an infinite distance away for us to look at, but at least be accurate.
This finite distance to the vanishing point
Have we established there is a finite distance to the vanishing point? We've established that humans can't perceive objects less than one minute of a degree in size. That's not the same thing. After all, a spot on an elephant may have vanished from naked-eye perception at a distance at which the elephant can still be seen. So it's not that perspective is different for the two; just that their size makes one of them imperceptible. (Of course, pull out a telescope and all of a sudden you can see them both again. Meanwhile perspective just stays the same as it always has).
is what allows ships to ascend into horizon and disappear as their hulls intersect with the vanishing point.
This
does not follow from the precepts laid out before. Even in Chapter 14, this key point is laid out very poorly. In essence, it says that at a great enough distance, it's hard to tell two things apart. Makes sense. It says a white mark on an object becomes essentially indistinguishable from the ground its resting on at enough of a distance. Right again. But what happens when you pull out your telescope again? You see the white mark just fine. It's no longer indistinguishable from the ground. Likewise, if you see a distant ship with its hull apparently below the water, you should pull out your telescope. If it's on a flat plane and your telescope is strong enough, it will be distinct from the water no matter how far away it is.
Every receding star and celestial body in the night sky likewise disappears after intersecting with the vanishing point.
Absolutely right. If something, even the size of a star, moves a far enough distance away, it will effectively reach the vanishing point and disappear. It will do so by becoming smaller as all of its points "crowd" in to that vanishing point.
Again, I don't care what people believe, but if you're going to have any hope of the scientific world taking you even somewhat seriously, then you can't promote erroneous ideas. At the very least get the science right.