Click here to see an example of a secure and flexible seat in trot. Watch closely as the rider's hips, pelvis, and legs flex freely with the horse's movement. Horse's willingly raise their back up under a seat like this, probably because it feels a bit like getting a gentle back rub with each step.
The celestial sphere is divided by the celestial equator. In astronomy and navigation, the celestial sphere is an imaginary sphere (ball) of a very large unspecified size. The sphere is concentric with the Earth. This means that the celestial sphere and the earth have the same centre. They also rotate upon the same axis.
The Wandering and Fixed Stars in the Celestial Region. In contrast to the terrestrial, the celestial region of the heavens had a fundamentally different nature. Looking at the night sky the ancient Greeks found two primary kinds of celestial objects; the fixed stars and the wandering stars. Think of the night's sky. Most of the visible objects appear to move at exactly the same speed and present themselves in exactly the same arrangement night after night.