Editing Unit of length (section)

===Astronomy===
{{main article|Astronomical system of units}}
[[Astronomy|Astronomical]] measure uses:
*[[Earth radius]] {{Earth radius}} ≈&nbsp;6,371&nbsp;km<ref name="Moritz2000">{{cite journal |last=Moritz |first=H. |date=March 2000 |title=Geodetic Reference System 1980 |journal=Journal of Geodesy |volume=74 |issue=1 |pages=128–133 |doi=10.1007/s001900050278 |bibcode = 2000JGeod..74..128. |s2cid=195290884 }}</ref>
* [[Lunar distance (astronomy)|Lunar distance]] ''LD''&nbsp;≈&nbsp;{{val|384402|u=km}}.<ref name="Apache Point">{{cite journal|last1=Battat|first1=J. B. R.|last2=Murphy|first2=T. W.|last3=Adelberger|first3=E. G.|title=The Apache Point Observatory Lunar Laser-ranging Operation (APOLLO): Two Years of Millimeter-Precision Measurements of the Earth-Moon Range|journal=Astronomical Society of the Pacific|date=January 2009|volume=121|issue=875|pages=29–40|doi=10.1086/596748|jstor=10.1086/596748|bibcode = 2009PASP..121...29B |doi-access=free}}</ref> Average distance between the center of Earth and the center of the Moon.
*[[astronomical unit]] au. Defined as {{val|149597870700|u=m}}.<ref name=Nature2012>{{cite web
 | url = http://www.nature.com/news/the-astronomical-unit-gets-fixed-1.11416
 | title = The astronomical unit gets fixed: Earth–Sun distance changes from slippery equation to single number.
 | author = Geoff Brumfiel
 | date = 14 Sep 2012
 | access-date = 14 Sep 2012
}}</ref>  Approximately the distance between the Earth and Sun.
*[[light-year]] ly&nbsp;≈&nbsp;{{val|9460730472580.8|u=km}}. The distance that light travels in a [[vacuum]] in one [[Julian year (astronomy)|Julian year]].<ref name="IAUgen">{{citation| url = http://www.iau.org/public_press/themes/measuring/ | title = The IAU and astronomical units | publisher = International Astronomical Union | access-date=2008-07-05}}</ref>
*[[parsec]] pc&nbsp;≈&nbsp;{{val|30856775814671.9|u=km}} or about {{val|3.26156|u=ly}}
*[[Hubble's law#Hubble length|Hubble length]] 14.4 billion light-years or 4.55 gigaparsecs