According to this size, an eight-foot-tall man is about 184 cm.
In modern times, one foot is equal to ten inches.
The length of one foot is different in different periods.
In Shang dynasty, one foot was16.95cm.
One foot 23. 1cm in the Zhou dynasty?
One foot in the Qin Dynasty was about 23. 1cm?
A foot in the Han Dynasty is about 2 1.35-23.75cm?
The reflection, one foot is 24.2cm today?
Southern dynasties, about 25.8cm a foot?
Northern Wei Dynasty, one foot is 30.9cm today?
Sui dynasty, one foot is 29.6cm today?
A foot 30.7cm in the Tang Dynasty?
One foot 3 1.68cm in Song and Yuan Dynasties?
Woodworking in Ming and Qing dynasties was 3 1. 1cm.
Extended data:
Modern commonly used length units:
(1) km
Kilometer, also known as kilometer, is a unit of length, abbreviated as "km", which is usually used to measure the distance between two places. The common conversion relationship is as follows: 1 km (km) = 1 0,000m (m) = 1 00,000m (cm) =10,000mm (mm); 1.6 1 km = 1 mile.
(2) meters
The unit of length "meter" in the international system of units originated in France. 1790 In May, a special committee composed of French scientists suggested that one fortieth of the total length of the earth meridian passing through Paris should be used as the unit of length-meter, and 179 1 year was approved by the French Parliament.
In order to make a benchmark to represent the value of rice, under the leadership of French astronomers Gerliangbule and Mishin, measurements were made from Dunkirk, France to Barcelona, Spain, and from 1792 to 1799.
1799, according to the measurement results, a short-section platinum rod of 3.5 mm× 25 mm was made, and the distance between the two ends of the rod was set as 1 m, which was kept by the French archives, so it was also called "archive meter". This is the earliest definition of rice? .
Due to the serious deformation of archival rice, 1872 abandoned the definition of archival rice and used rice made of original platinum alloy (90% platinum, 10% iridium) as the length unit.
The original rice cooker was made according to the length of the "file rice". At that time, * * * made 3 1 piece, the cross section was approximately X-shaped, and the length of the archive meter was engraved on the groove (neutral surface) of the ruler with two 6-8 micron wide scribes.
1889 At the first international metrology conference, the prototype of No.6 rice identified by the International Bureau of Metrology (one of the prototype of 3 1 meter which is closest to the length of the file rice at 0℃) was selected as the international rice prototype, which was kept as the length benchmark in the basement of the International Bureau of Metrology in Paris, and the remaining rulers were distributed to the participating countries as auxiliary rulers.
It is stipulated that when the ambient air temperature is 0℃, the distance between the two ends of the rice cooker is 1m. 1927. The definition of rice was strictly stipulated in the Seventh International Metrology Conference. In addition to the temperature requirement, it is also proposed that the raw rice container should be kept at the standard atmospheric pressure 1, and its placement method is specified in detail.
However, there are many shortcomings in using rice calibrator as the objective standard of rice, such as the low accuracy of material deformation measurement (only 0. 1μm), which is difficult to meet the needs of precise measurement such as metrology.
In addition, if the original rice cooker is damaged, there will be no basis for copying, especially it is difficult to ensure that the replica is completely consistent with the original rice cooker, which brings difficulties to the use of various countries. Therefore, the idea of using natural values as unit benchmarks has always been desired by people.
In 1950s, with the development of isotope spectrum light source. The narrow Krypton -86 isotope spectrum was discovered. With the success of interference technology, people finally found a natural standard that is not easy to be destroyed, that is, the natural standard with the wavelength of light wave as the length unit.
This natural benchmark has stable performance, no deformation problem, easy replication and high replication accuracy. China also established the krypton -86 isotope length standard in 1963.
After the definition of rice is changed, the original international rice instruments are still kept in the International Bureau of Metrology according to the original regulations. With the progress of science and technology, since the 1970s, the measurement of time and the speed of light has reached a high precision.
Therefore, 1983, 10 adopted a new definition of the meter at the 17th international metrology conference held in Paris in June: "the meter is the length of light propagating in a vacuum with a time interval of 1/299792458 seconds". In this way, the definition of meter based on spectral line wavelength is replaced by the new definition of meter.
(3) decimeter
Decimeter or dm is one of the metric units of length, and 1 decimeter is equivalent to one tenth of 1 meter. The common conversion relationship is as follows: 1 decimeter = 0.000 1 kilometer (km) = 0. 1 meter (m) = 10 centimeter (cm) = 100 millimeter (mm).
4) cm
Centimeter, unit of length; Chinese: centimeter (s), abbreviated as cm. The unit conversion of centimeters is as follows:1cm =10 mm = 0.1decimeter = 0.0 1 m = 0.0000 1 km.
(5) mm
Millimeter, also known as millimeter (or millimeter), is a unit of length and rainfall, and the symbol is ㎜. 1mm is equivalent to one thousandth of 1mm (this means "milli"). The decimal relation is as follows:1mm = 0.1cm = 0.01decimeter = 0.001m = 0.000001km.
Baidu Encyclopedia _ One Foot
Baidu Encyclopedia _ Length Unit