The clock is a timing device and a precise instrument for measuring and indicating time. Clocks are usually distinguished by the size of the internal machine. According to international practice, clocks and watches with a movement diameter greater than 80 mm and a thickness greater than 30 mm; A pocket watch with a diameter of 37 ~ 50 mm and a thickness of 4 ~ 6 mm is called a pocket watch;

Watches with a diameter less than 37 mm; A watch whose diameter does not exceed 20mm or whose movement area does not exceed 3 14m2 is called a women's watch. The watch is one of the smallest, strongest and most sophisticated machines invented by human beings.

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Many people have always believed that clocks and watches originated in foreign countries. In fact, it was China's clock technology that was first introduced to Europe, and Europeans later made clocks with excellent workmanship. When it comes to clocks and watches in China, many people's first reaction may be sundials, water clocks and so on. However, these ancient timing tools can not be called clocks strictly, but only timers.

In the Swiss World Watch Magazine, it was recorded that "the escapement used in modern mechanical clocks originated from the invention of ancient Su Song in China", and Needham, a famous British historian of science and technology, said, "Since Su Song combined clock machinery with astronomical observation instruments,

In principle, he has succeeded completely. He was six centuries earlier than Pei and Hooke, the inventors of western astronomical clocks, and seven and a half centuries earlier. "1099, Su Song, the prime minister of the Northern Song Dynasty, presided over the construction of a water transport instrument like a modern clock, with a daily error of only one second.

Reference source; Baidu encyclopedia-clocks and watches