The Instrument Rating gives the ability to control the aircraft without reference to the ground or horizon, using flight and navigation instruments.
仪表等级赋予飞行员控制飞机的能力，而不用参考地面或地平线，只使用飞行和导航仪表。
2
In a moving train one feels out of balance, the earth seems to be constantly moving and your mind has only the horizon as a reference, all the others things are constantly in motion.
Thomas suspects that the horizon provides a helpful point of reference, allowing people to sense the difference between their body's natural motion and the motion of the ship.