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 point in the sky that corresponds to the Earth's North Pole, around which the Celestial Sphere therefore appears to rotate. It is not a fixed point in the sky, but it currently lies close to the star Polaris in Ursa Minor. A point in the sky that corresponds with Earth's own North Pole.