Thanks to everyone,
"The Horizon is frame of reference only for the aircraft you are in."
Ok, so it is basically only a line which tells you if you are going up or down. In the blue part, you are climbing, and in the brown part, you are going towards the ground, so descending.
Wikipedia: "The horizon (or skyline) is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not."
So the horizon, of a plane is not at all related to this one! Because, if it shows that we are below Horizon, it would mean that we are on ground level!
The pitch is calculated with the "artificial" horizon, not the "wikipedia's" one, am I right?
Thanks,
AF330
PS: "Meanwhile, in other threads he's asking about Alpha floor, autothrust et al..." Ok, Amadis of Gaul... I didn't really get your post... Still, thanks for posting this!