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A light-year, alternatively spelled light year (ly or lyr[3]), is a unit of length used to express astronomical distances and is equal to exactly 9,460,730,472,580.8 km (Scientific notation: 9.4607304725808 × 10 12 km), which is approximately 5.88 trillion mi.
The centimetre (SI symbol: cm) is a unit of length in the metric system equal to 10−2 metres ( 1 100 m = 0.01 m). To help compare different orders of magnitude, this section lists lengths between 10 −2 m and 10 −1 m (1 cm and 1 dm). 1 cm – 10 millimetres. 1 cm – 0.39 inches. 1 cm – edge of a square of area 1 cm 2.
From 1630 to 1718 a millia was 5,564 feet (1,696 metres), making a geographical league of four millias equal 22,256 feet (6,784 m or 3.663 modern nautical miles). But from 1718 through the 1830s the millia was defined as the equivalent of just over 5,210 feet, giving a shorter geographical league of just over 20,842 feet (6,353 m or 3.430 ...
Under the Tang dynasty (AD 618–907), the li was approximately 323 meters. [citation needed] In the late Manchu or Qing dynasty, the number of chi was increased from 1,500 per li to 1,800. This had a value of 2115 feet or 644.6 meters. In addition, the Qing added a longer unit called the tu, which was equal to 150 li (96.7 km).
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute ( 1 / 60 of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).
The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in one second, and is equal to exactly 299 792 458 m (approximately 983 571 055 ft or 186 282 mi). Just as the second forms the basis for other units of time, the light-second can ...
3.261 56 ly. The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles). [a] The parsec unit is obtained by the use of parallax and trigonometry ...
The data mile is used in radar-related subjects and is equal to 6,000 feet (1.8288 kilometres). [90] The radar mile is a unit of time (in the same way that the light year is a unit of distance), equal to the time required for a radar pulse to travel a distance of two miles (one mile each way). Thus, the radar statute mile is 10.8 μs and the ...