Editing Speed of light (section)

=== Distance measurement ===
{{Main|Distance measurement}}
[[Radar]] systems measure the distance to a target by the time it takes a radio-wave pulse to return to the radar antenna after being reflected by the target: the distance to the target is half the round-trip [[Radar#Transit time|transit time]] multiplied by the speed of light. A [[Global Positioning System]] (GPS) receiver measures its distance to [[GPS satellites]] based on how long it takes for a radio signal to arrive from each satellite, and from these distances calculates the receiver's position. Because light travels about {{val|300000|u=kilometres}} ({{val|186000|u=miles}}) in one second, these measurements of small fractions of a second must be very precise. The [[Lunar Laser Ranging experiment]], [[radar astronomy]] and the [[Deep Space Network]] determine distances to the Moon,<ref name=science265_5171_482>
{{Cite journal
 |last=Dickey |first=J. O.
 |title=Lunar Laser Ranging: A Continuing Legacy of the Apollo Program
 |journal=Science | volume=265 | issue=5171
 |pages=482–490 |date=July 1994
 |doi=10.1126/science.265.5171.482
 |bibcode=1994Sci...265..482D | pmid=17781305|s2cid=10157934
 |display-authors=etal|url=https://trs.jpl.nasa.gov/bitstream/2014/32452/1/94-0193.pdf}}</ref> planets<ref name=cm26_181>{{Cite journal
 |last=Standish |first=E. M.
 |title=The JPL planetary ephemerides
 |journal=Celestial Mechanics |volume=26 |date=February 1982
 |issue=2 |pages=181–186 |doi=10.1007/BF01230883
 |bibcode=1982CeMec..26..181S |s2cid=121966516
}}</ref> and spacecraft,<ref name=pieee95_11_2202>
{{Cite journal
 |last1=Berner |first1=J. B.
 |last2=Bryant |first2=S. H.
 |last3=Kinman |first3=P. W.
 |title=Range Measurement as Practiced in the Deep Space Network
 |journal=Proceedings of the IEEE |date=November 2007 |volume=95 |issue=11 |pages=2202–2214
 |doi=10.1109/JPROC.2007.905128 |s2cid=12149700
 |url=https://trs.jpl.nasa.gov/bitstream/2014/40972/1/07-0166.pdf}}
</ref> respectively, by measuring round-trip transit times.