What is the horizon? Why can’t you reach it?

If you stand on some kind of hill (hill, mountain, or even the top floor of a high-rise building), then you can see a rather large distance around. At the farthest point, there will be a feeling that heaven and earth are merging together. This is the concept of the horizon. The higher a person is, the further the horizon line moves away from him. And you cannot reach this line, because it moves with the observer. A person cannot catch up with the horizon, since the horizon is not a specific point, but a visual effect.