When watching the 100-meter race on TV, we often think that athletes run very fast, but in fact they are always on the screen. Why is this?

Explain it with the relativity of motion. Taking the camera (TV screen) as the reference object, the camera and the athlete move at the same speed, and the position between them is almost unchanged, so the athlete is relatively static, so the athlete is always on the screen; Taking the ground as a reference, the position between the two changes, and the athletes are moving, so they feel that the athletes are running fast.