The doors and windows of buildings are usually designed as rectangles, and the ratio of short sides to long sides is 0.6 18, which gives people a sense of stability and harmony. The ratio between the lower part and the upper part of the second platform of the famous Eiffel Tower and the length ratio between the upper part and the lower part of the magnificent Toronto TV Tower is also 0.6 18. The first pyramid in Kisha, Egypt, is 146 meters high and 230 meters long at the bottom, and the ratio is also close to 0.6 18, giving people a magnificent feeling. Phippos, an Italian, found that the length from the navel to the navel is about 0.6 18. In addition, the length from head to throat to navel, and the length from knee to sole to knee are also 0.6 18. Not all people fully meet this ratio, but anyone who meets it can give people a sense of lightness and symmetry. It has also been found that the weight of erhu is beautiful at 0.6 18 of the chord length; When the room temperature is around 23℃ in winter, residents feel comfortable, and its ratio to human body temperature is just close to 0.6 18. It's amazing. 0.6 18.