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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 kilometre (SI symbol: km) is a unit of length in the metric system equal to 1 000 meters (10 3 m). To help compare different orders of magnitude , this section lists lengths between 1 kilometer and 10 kilometers (10 3 and 10 4 meters ).
The refractive index of air is approximately 1.0003. [65] Denser media, such as water, [66] glass, [67] and diamond, [68] have refractive indexes of around 1.3, 1.5 and 2.4, respectively, for visible light. In exotic materials like Bose–Einstein condensates near absolute zero, the effective speed of light may be only a few metres per second.
As in Greek, the number "ten thousand" is used figuratively in Chinese to mean any "immeasurable" value and this title has never provided a literal distance of 10,000 li (5,000 km or 3,100 mi). The actual length of the modern Great Wall is around 42,000 li (21,000 km or 13,000 mi), over 4 times the name's proverbially "immeasurable" length.
It has a nearly round shape with the diameter varying between 11 and 18 km (6.8 and 11.2 mi) and giving an average value of 15 km (9.3 mi). [ 5 ] [ 14 ] The shores are winding and contain many small bays; there are many small sandy islands ( noko ), rocks and coral reefs off the coast with the size up to 600 m (2,000 ft). [ 3 ]
At IUPAC standard temperature and pressure (0 °C and 100 kPa), dry air has a density of approximately 1.2754 kg/m 3. At 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m 3. At 70 °F and 14.696 psi, dry air has a density of 0.074887 lb/ft 3.
The 38th parallel north is a circle of latitude that is 38 degrees north of the Earth's equatorial plane.It crosses Europe, the Mediterranean Sea, Asia, the Pacific Ocean, North America, and the Atlantic Ocean.
As one degree is 1 / 360 of a circle, one minute of arc is 1 / 21600 of a circle – such that the polar circumference of the Earth would be exactly 21,600 miles. Gunter used Snellius's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude.