In my earnest desire to comprehend flat-Earth cosmology, I must ask, "Am I right in thinking that in flat-Earth cosmology, the following things are both claimed:
a) The sun revolves around a line intersecting the north pole (which is at the center of the disc of the Earth) perpendicularly;
If that were true, the sun would rise and set in the North Pole.
No, the sun obviously moves around the Earth, over the Equator.
b) The sun remains above the disc of the Earth, and never intersects the plane in which the disc of the Earth lies.
Correct. It is always above the equator somewhere.
And if the answer to this question is "yes", then why do we see sunrises and sunsets?
Well, obviously, the sun appears at a grater angle when it's not over you.
View this kick-ass graphic I just made using Photoshop.
Soak it in... Does my Photoshop abilities astound you? Well, they shouldn't. :p Anyway, now, the sun is going to look a lot lower in the sky to someone in the right side of my simplified map. To those on the left, though, it looks noonish.
Of course, that doesn't explain actual setting. The answer is simple: gravity.
Yup. Gravity pulls everythign down, including light, right? Right.
So my explanation is really simple when you think about it.
Now, I'm going to add some more stuff to my crappy picture. But it will BLOW YOUR MIND!
Is your mind blown yet? No? I guess I need to work on my Photoshoping. Please remember it isn't even remotely to scale. Or anything. Just a helpful illustration. Anyway, light (represented here by crudely drawn yellow lines) is pulled down by gravity. In fact, this same effect is what causes our blue sky (it affects different wavelenghts differently, dispersing the blue light in the atmoshpere. It's also the reason you see a lot redder sunsets - that light has traveled through more atomoshpere, so all the smaller wavelenghts have been diffused, leaving red - the longest visible wavelength - predominant). Anyway, I'm getting off track.
Light coming from the sun is hurled out like a baseball, and it can only travel so far before it must land. People outside of the zone that can see the sun's light get night time, since the light couldn't travel that far. On my crappy drawing, people right of point A are expereincing the night.
But still, you say,
how does the sun set? You havnen't answered that one yet! Quit dodging the question! To which I respond: Hey! Rhetorical voices shouldn't be so rude. Sit down, I'm about to explain it.
Here's the deal: imagine you're standing at Point A, and the sun is slowly moving to the left. The rays of light eminating from the lower altitude portions of the sun can't reach you, but the ones juuuuust from the top can. As the sun moves further away to other parts of the Earth (here represented by moving to the left), you can see less and less, until you can only see the tippy top... and then it disappears too! Viola, sunset!
Of course, for a sunrise, it's just reversed. You see the top first, as the sun gets closer, until eventually all the rays of light, revealing the sun from the top down, for a sunrise.
If the answer is "no", please specify in which claim(s) (a or b) my understanding is flawed.
There ya go!