In order to keep the balance of an object, its line of gravity must pass through the supporting surface, otherwise, the object will fall down. Therefore, acrobats who walk a tightrope should always let their gravity action line pass through the tightrope. However, because the tightrope is very thin, it is difficult to make the body center of gravity fall on the tightrope, and the body is in danger of falling at any time. Life experience tells us that when the body is shaking and falling, people often swing their arms to regain their footing. The swing of the arm is to let the gravity line pass through the support surface to restore balance. Gymnasts often do this on the balance beam. Acrobats walk a tightrope, of course, they have to swing their arms left and right to grasp the center of gravity and maintain balance. The flower umbrella, colorful fan or bamboo pole they hold plays the role of "stretching their arms" and is an auxiliary tool to help their bodies balance.
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