Título: Shen Kuo
Seção: Magnetic needle compass
Background: Shen Kuo (Chinese: Chen Gua ; 1031-1095), courtesy name Cunzhong (Cun Zhong ) and pseudonym Mengqi (now usually given as Mengxi) Weng (Meng Xi Weng ), was a Han Chinese polymathic scientist and statesman of the Song dynasty (960-1279). Excelling in many fields of study and statecraft, he was a mathematician, astronomer, meteorologist, geologist, zoologist, botanist, pharmacologist, agronomist, archaeologist, ethnographer, cartographer, encyclopedist, general, diplomat, hydraulic engineer, inventor, academy chancellor, finance minister, governmental state inspector, poet, and musician.

Conteúdo: Since the time of the engineer and inventor Ma Jun (c. 200-265), the Chinese had used the south-pointing chariot, which did not employ magnetism, as a compass. In 1044 the Collection of the Most Important Military Techniques (Wu Jing Zong Yao ; Wujing Zongyao) recorded that fish-shaped objects cut from sheet iron, magnetized by thermoremanence (essentially, heating that produced weak magnetic force), and placed in a water-filled bowl enclosed by a box were used for directional pathfinding alongside the south-pointing chariot.  However, it was not until the time of Shen Kuo that the earliest magnetic compasses would be used for navigation. In his written work, Shen Kuo made the first known explicit reference to the magnetic compass-needle and the concept of true north. He wrote that steel needles were magnetized once they were rubbed with lodestone, and that they were put in floating position or in mountings; he described the suspended compass as the best form to be used, and noted that the magnetic needle of compasses pointed either south or north. Shen Kuo asserted that the needle will point south but with a deviation, stating "[the magnetic needles] are always displaced slightly east rather than pointing due south."  Shen Kuo wrote that it was preferable to use the twenty-four-point rose instead of the old eight compass cardinal points -- and the former was recorded in use for navigation shortly after Shen's death. The preference of use for the twenty-four-point-rose compas

user: What is significant about the magnetic needle compass?

assistant: Shen Kuo made the first known explicit reference to the magnetic compass-needle and the concept of true north.

user: Did he invent it?

assistant: The preference of use for the twenty-four-point-rose compass may have arisen from Shen's finding of a more accurate astronomical meridian,

user: What is important about his reference to the compass during that time?

assistant: when Shen Kuo was writing the Dream Pool Essays; this meant that in Shen's time the compass might have already been in navigational use.

user: What were the Dream Pool Essays?

assistant: Shen Kuo's writing on magnetic compasses

user: What else did he say about the magnetic compasses?

assistant: He wrote that steel needles were magnetized once they were rubbed with lodestone,

user: Is the location with a magnetized compass more accurate?

assistant: stating "[the magnetic needles] are always displaced slightly east rather than pointing due south."

user: Was there anything Shen disliked about magnetic needle compasses?

assistant: CANNOTANSWER