How does the artificial horizon on the plane work then? I'm really curious.,(reply>), +Papooch They are generally a gyroscope, a spinning disk that remains level because that is what spinning disks do. They are usually biased in some way so that they will slowly respond to changes in the apparent gravity force - if they didn't, they'd always maintain the horizon of where you took off, which wouldn't be that useful once you flew a quarter of the way around the world!,(reply>), @Papooch they can messure the force and calculate that it can't be only because of earth gravity and so they can calculate the ouward accileration. Basicly the have scale witch shows a higher weight when he goes into a curve. But it is to low for sitting person to feel.