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The nanometre (SI symbol: nm) is a unit of length in the metric system equal to 10 −9 metres ( 1 / 1 000 000 000 m = 0. 000 000 001 m). To help compare different orders of magnitude, this section lists lengths between 10 −9 and 10 −8 m (1 nm and 10 nm). 1 nm – diameter of a carbon nanotube
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).
Length; Name of unit Symbol Definition Relation to SI units ångström: Å ≡ 1 × 10 −10 m: ≡ 0.1 nm astronomical unit: au ≡ 149 597 870 700 m ≈ Distance from Earth to Sun
The siriometer is an obsolete astronomical measure equal to one million astronomical units, i.e., one million times the average distance between the Sun and Earth. [13] This distance is equal to about 15.8 light-years, 149.6 Pm, or 4.8 parsecs, and is about twice the distance from Earth to the star Sirius. [14]
A barn (symbol: b) is a metric unit of area equal to 10 −28 m 2 (100 fm 2).This is equivalent to a square that is 10 −14 m (10 fm) each side, or a circle of diameter approximately 1.128 × 10 −14 m (11.28 fm).
watt per square metre per hertz W⋅m −2 ⋅Hz −1: M⋅T −2: Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m −2 ⋅nm −1. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity". M e,λ [nb 4] watt per square metre ...
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In ordered solids, the atomic spacing between two bonded atoms is generally around a few ångströms (Å), which is on the order of 10 −10 meters (see Lattice constant). However, in very low density gases (for example, in outer space ) the average distance between atoms can be as large as a meter .