Experiment to calculate earth radius (Proving it's a sphere).

I posted this in another topic, but since it was not relevant with the topic itself I tough it would be better to post this in the forum section for debates and with a proper topic. Well here's the point, this PDF explains that you can calculate the earth radius by watching the sunset, take a look: PDF Article, so if you can calculate the radius like that, that means the earth is a sphere, not a plane. What do you flat earth believers think about this?

Radius is not exclusive to spheres.

Yes, a cicle clan have radius too, but you can't view 2 sunsets in a circle unless you get too high; the PDF have a image explaining that.

The horizon recedes as the observer gains altitude. This is simple perspective. It does not require the earth to be a sphere.

Did anybody read the PDF? Yes, you need the earth to be a sphere to do that, unless the sun rotates around the earth, maybe some flat earth models think that...

Did anybody read the PDF? Yes, you need the earth to be a sphere to do that, unless the sun rotates around the earth, maybe some flat earth models think that...

No, you do not. As you gain altitude the atmolayer becomes thinner, hence you can see it when it is farther away, giving the illusion of a moving horizon.

I don't think it has anything to do with the atmoplane. It is simple perspective.

Ski is correct. It's a perspective effect.

I asked if you read the PDF because there's a image explaining "the perspective effect", thanks to the earth is a sphere we can do that, but if it was a plane the horizon would not change very much with the height:
The black lines represent some of the possible views, in a flat earth model, the earth form is does not block your line of view, so small height changes would not affect the horizon very much. In the round earth the line of view can be blocked by the earth form itself so it can hide the sun.