The conversion of the metrological system: How long was the hair of Li Po?
Q: The poetic god, Li Po, wrote in his Songs of Qiu-Pu, "My hair is three thousand zhangs (a measurement unit) in length, but my worry is even longer; I wonder from where the autumn frost in the mirror comes?" (Autumn frost symbolizes the white hair). What is the exact length of the three-thousand-zhang-long white hair of Li Po?
A: In the ancient Chinese metrological system, one zhang is equal to ten chis. According to the "History of Chinese Metrology" written by Wu Cheng-luo (1998: 65), in the Tang dynasty of Li Po, one chi was about 31.1 cm, and one zhang was 311 cm, i.e. 3.11 meters; therefore, the length of Li-Po's hair is 9,330 meters (3.11 m × 3,000), which is more than nine kilometers. However, this is a frequently used hyperbole in literature (Hyperbole: extravagant and exaggerated rhetoric). Of course, it was impossible that the hair of Li-Po could be that long.
