""refers to the distance between the ends of the thumb and middle finger.
Step: In ancient times, it was a unit of length. The ancients took once as a step and twice as a step. Now people often say how many steps they have taken when measuring distance.
Extension: refers to the distance between the hands of adults when their arms are horizontally extended, which is about five feet.
Extended data
The traditional units of length in China include Li, Zhang, ruler, inch, ten-day, festival, happiness, straightness, righteousness, length, Asia, extension, Kyrgyzstan, railway, Romania, millimeter, Li and minute.
"Bu", "Bu" and "Dong" are ancient units of length in China. The unit of length we use every day is the legal unit of length measurement in China, which is consistent with the international system of units. The standard unit of length is "meter", which is represented by the symbol "m".
1960 The 1st International Metrology Conference: "The length of the meter is equal to 1650763.73 times of the radiation wavelength passing between 2P 10 and 5d 1 levels of krypton -86 atoms in vacuum". Since 1983, the length of meter has been defined as "the distance that light travels in vacuum in 1/299 792 458 seconds.
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