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The li has varied considerably over time but was usually about one third of an English mile and now has a standardized length of a half-kilometer (500 meters or 1,640 feet or 0.311 miles). This is then divided into 1,500 chi or "Chinese feet".
The largest unit for expressing distances across space at that time was the astronomical unit, equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660 000 astronomical units (9.9 ...
kilometre (km) or kilometer is a metric unit used, outside the US, to measure the length of a journey; the international statute mile (mi) is used in the US; 1 mi = 1.609344 km; nautical mile is rarely used to derive units of transportation quantity.
The basic unit of length in the imperial and U.S. customary systems is the yard, defined as exactly 0.9144 m by international treaty in 1959. [2] [5] Common imperial units and U.S. customary units of length include: [6] thou or mil (1 ⁄ 1000 of an inch) inch (25.4 mm) foot (12 inches, 0.3048 m) yard (3 feet, 0.9144 m)
The Roman mile (mille passus, lit. "thousand paces"; abbr. m.p.; also milia passuum [n 2] and mille) consisted of a thousand paces as measured by every other step—as in the total distance of the left foot hitting the ground 1,000 times. [9] When Roman legionaries were well-fed and harshly driven in good weather, they thus created longer miles.
A metric lieue was used in France from 1812 to 1840, with 1 metric lieue being exactly 4,000 m, or 4 km (about 2.5 mi). [4] It is this unit that is referenced in both the title and the body text of Jules Verne's novel Twenty Thousand Leagues Under the Seas (1870). [5]
To help compare different orders of magnitude, this section lists lengths between 10 −3 m and 10 −2 m (1 mm and 1 cm). 1.0 mm – 1/1,000 of a meter; 1.0 mm – 0.03937 inches or 5/127 (exactly) 1.0 mm – side of a square of area 1 mm²; 1.0 mm – diameter of a pinhead; 1.5 mm – average length of a flea [27]
For example, 10 miles per hour can be converted to metres per second by using a sequence of conversion factors as shown below: = . Each conversion factor is chosen based on the relationship between one of the original units and one of the desired units (or some intermediary unit), before being rearranged to create a factor that cancels out the ...